Modified pattern to work the heels in-the-round instead of working flat to avoid seam ridges at the heel.

Magic CastOn 15 sts per needle starting at Chart row 28.

Yarn amount: 50g each (105 yds each)

Followed chart rows 28-47, working both directions from the base of the heel, increasing to a total of 66 sts.

Modified chart to work increases 1 stitch in from sides.

Backwards Loop Increases
a.k.a. E. Zimmermann M1 Increases R & L:
http://www.craftsfromthecwtch.co.uk/2015/11/a-perfectly-e…
http://knittingnuances.com/resources/Tutorials/Make1Loop.pdf

Remember on the next row when working the increased sts, to work the right leaning backwards loop increase through the back loop or the increased stitch comes undone: You can recognize the backwards loop increase st that needs to be worked through the back loop by noticing the loop is reverse mounted. http://chezlizzie.blogspot.com/2013/02/the-backward-loop-…

Tip to Make SSK Decreases tidier and better match to the K2tog Decreases in the Toe Area
On the row before the Decrease row, wrap opposite way the two sts that that will be used for the SSK. The stitches will have reverse mount and can be knitted through the back loop on the Decrease round. This allows you to skip the slipping the two sts that often cause the loops to enlarge. Or just work on the needle tips and be careful to not stretch the loops when slipping.

After working 33 sts across Row 48, knit sts 34-66 on scrap for opening.

Modified pattern to work a Central Double Decrease instead of a Left Leaning Double Decrease used in the pattern.

Central Double Decrease: slip 2tog knitwise, knit 1, pass the 2 slipped sts tog over the new knit stitch. Results in decrease looking symmetrical about the center stitch with the stitch on either side being decreased and tucked behind.
https://youtu.be/9oBQLjfcXrY

Left Leaning Double Decrease: slip 1 stitch knit wise, knit 2 together, and pass the slipped stitch over the knit stitch. Results in a mitre looking decrease.

Right Leaning Double Decrease: k2tog tbl (like ssk). Slip stitch back to left needle. Pass next stitch over. Slip stitch back to right needle. (Substitute k3tog if desired.)

Finishing w Tvinnarand Braid
The slippers are finished with a Tvinnarand Braid around the opening. The Tvinnanard Braid is worked exactly like the Latvian Braid except that the two braid rows are worked through reverse mounted stitches.

The color of yarn you use for the set up round for either the Tvinnanard or Latvian Braid will form the center line between legs of the braid. I’m alternating between MC and CC on the set up round so the center horizon bars match the alternating colors of the legs of the braid.

I’m also decreasing the stitch count by 8% during the set up round before beginning the two rows of braid to draw the edge in slightly.

Tvinnarand Braid
From pattern: ”Tvinnarand Braid is like the Latvian braid except you twist the purl stitch by bringing the working yarn under the needle.”
Pick up and knit 49 sts from the original 61 cast on sts. The video shows the picked up and knit stitches with normal mount. I picked up and knitted these sts for the set up row with a reverse mount so the first braid row is worked through reverse mount loops just like the second row of the braid shows in part 2 of the video.
Bring both yarns to the front, insert needle tip purlwise, wrap under the needle (will make reverse mount) and draw through to make purl stitch. Then twist strands counterclockwise bringing new color under old. Continue to end of round keeping working strands with firm tension.
https://youtu.be/jio3tcAf9h4

On second round, the loops sitting on left needle are reverse mount, insert needle purlwise through front leg of the reverse mount loop and purl the stitch. Then twist strands clockwise to bring new color up for next stitch.
https://youtu.be/DSTVjO7nWeY

After second round of braid, (with background color) use Standard Bind Off, knitwise through front leg of the reverse mount stitches.
https://youtu.be/Gi3zOvrJeRU

Latvian Braid
Stitch count for the braid is 8% fewer sts than total stitch count before or after braid. On preparation round I will knit in alternate colors for each stitch and decrease evenly 6 sts to end with a even number of 60 sts (30 instep and 30 heel sts)
Preparation rnd: K 1 rnd. In the 2 colors of your braid or in an entirely different color(s). Keep in mind that what color yarn(s) you use on this rnd will form the center line of your finished braid.
Braid rnd 1: Bring both colors forward so they are hanging outside the circle. Pull about 2 yards free from both skeins of your braid colors.* P 1 st cc1, then bring cc2 over cc1 and purl 1 st cc2. Repeat from star to end of rnd, always bringing the next color over the last color wked. This will twist the 2 yarns as you p around the circle.
To keep the yarn from snarling as you work, push twists back toward skeins as you purl. When the rnd is complete, a 2 color twisted cord hangs from your work.
Braid rnd 2: Now, * p 1 cc1, then bring cc2 under and p 1. Repeat from star but this time always bringing the following color under the color just wked. At the end of the rnd, the twists will be undone and you braid will be complete!

I chose to maneuver the two working strands with my right hand to help make a tidier braid.
Here’s a video showing a good tensioning Method on the Latvian Braid: https://youtu.be/S1wmXYBIEAs

Master Knitter, Arenda Holladay, on tensioning purl stitches (a problem more common with Continental knitting) so I will hold working yarn in right hand when purling for the braid stitches.
By the way….Arenda and Kristin both prefer to work stranded colorwork flat.
http://www.arendaholladay.com/search?q=Purl+continental+K...

Finished slipper dimensions
Modified heel has 21 rounds= 2.75” heel ht
Slipper width (33 sts) = 4.5”
Total slipper length 66rounds from back of heel to tip of toe is 66 rounds= 9.375”
Top of slipper length= 6.5”

Notes while researching other Techniques for Scandinavian Slippers:

2-Color Cast-ons: slip knot with both colors.
1.JBMCO with MC over index finger: MC cast-on loops will form on bottom needle and be first half rnd when knitting
When done co, rotate needles and bring MC left to right in front of CC and to back to beg knitting into MC loops to catch the CC yarn.knit across with MC. Then remove slip knot and work across second needle.
1. Figure-8 CO hold needles parallel in left hand so the tips point to the right and the slip knot is on top needle. Wrap the twin yarn in front of bottom needle, up through center and around top needle, up through center, and around botttom needle while keeping the colors in the newly formed loops alternating. If you need an odd number of sts, wrap the single yarn one more time in a figure 8 in MC if the MC was the very first loop.

For casting on socks with two colors, make slip knot with both colors and place on top needle with needle held in RH. Have MC over index finger to have the MC form the edge line and the CC over thumb forms the loops.

Blanket-stitched edge for socks:
CO in two colors with with LTCO or GTCO.
Slip the first stitch pw, join in round, twine knit, alternating colors for first rnd. Twine knit into first st of the second rnd then twine purl around. Switch to two strands of the same color and twine knit the next 3 to 5 rounds in one color.

Avoid jog where there is new color or change of stitch pattern by slip first stitch of the new color/pattern round. In the next round knit or purl according to pat into the slipped st.

Twine knitting. Twinning is often done in alternating colors; Twin every 2 or 3 sts across a region of same color.
Knit a st, then the next color needed is brought OVER the top of the previous color to knit the next stitch
Twine Purl. Both color yarns are in front. Purl. Then bring the strand of the next color needed UNDER the previously used strand.

When fixing mistakes after laddering down, catch the strand of the color you need or the double strands are in the same color, hook the longer strand to draw through the loop.

To keep order while untwisting 3 colors of twinned knitting balls of yarn, keep pattern ball in left hand and the 2 CC held in the right hand.

Use twine sts on heel, instep and toe for strtchiness.
Use stranded method on sole for durability.

With worsted weigh, US4, gauge 7stsx7rnds per in.
CO 13 sts per 2 needles w dark MC over thumb to edge sole in dark color and heel in light edge. Turn. Light loops on top for heel.
Rnd1: Heel N1: (TK1 CC, tk1 mc) rep. Remove slip knot.
Sole N2: (TK1 mc, TK1 cc) rep
Rnd 2:Heel N1 incr rnd: (TK1 mc, rli cc, alt colors, tk to 1 st before end, LLP cc, tk1- 15 sts
Sole N2: (tk1 cc, tk1 mc) rep
Rnd3 and odd rnds: (tk1 mc, tk1 cc) rep
On alt rnds for stripe pat, there will be 2 sts of same color. Second incr in sequence will be made bet these 2 sts w alt color to maintain stripes.
Rep incr rnd followed by even rnd until 31 sts or 33 sts per needle.
for W7/8 M 8/9

After knitting in the waste yarn with MC to hold sts at opening, use twine knit for one round instead of stranded knitting to make it easier to pick up the held sts.

Foot: outer edge instep are MC and outer edge of sole are CC sts.
Rnd1 N1 instep: alt single check, beg and end with mc.
N2 sole alt single stripe, beg and end cc.
Rnd 2 n1 instep: K1 mc twice, (k1cc, k1 mc) rep to last 2 sts, k1 mc twice.
N2 sole: follow est pat for stripe.
Rep rnds1&2/for 30 rnds.

Toe: 2 sts same color will fall next to each other. On next decr they will be knit tog. Follow strip pattern: (tk1, stk, tk to last 3 sts of n1, tk2tog, tk1) rep to end of n2.
Rep decr rnd until 5/sts rem on each needle. Work sl1-k2tog-peso on center 3 sts. 3 sts rem on each needle. Cut yarns. Sl1 strand through rem loops and tighten. Weave in ends.
Ankle gap can be worked in two strands of mc or cc for solid color wedge or work as checkered pat.
Ankle opening: p/u one sole st at each end of the held sts. Pick up held sts through the right leg without rotating slipper before removing waste yarn from center-outward, leaving two waste yarn sts at each end to keep corners tighter while working the cuff. Then work a gusset of short rows over the p/u sole sts at the edges. Arr sts on the two cable needles so rnds start at center of heel (n1) and center of instep (n2). St number is uneven.
N1: 19 sts on heel and 15/sts on instep
N2: 18 sts on instep and 17 sts on heel.
Needle 1:
Row1: Beg at center heel, alt mc and cc in pat, tk across heel to to instep, tk2/sole sts tog that were the extra sts p/u bet heel and instep, tk2, turn, pm.
Row2: Slip 1, tp4 sts, , tpt2tog, turn, pm.
Row3: Sl1, tk to 1 st before marker, remove marker, sl st back, tk2tog tbl, turn, pm.
Row4: Sl1, tp to 1 st before marker, remove marker, sl st back, tp2tog, turn, pm.
Row5: Sl1, tk to 1 st before marker, remove marker, sl st back, tk2tog tbl, tk to end of n1.
Needle 2: Rows 1-4 same as N1.
Row5: Tk to center back of heel. To even pat, tk2tog across ankle gap.
Cuff: alt 1 rnd tk and 1 rnd tp
Rnd1 N1: Tk to 1 st before marker, remove marker, tk2tog across gap. Resume twined knitting on both needles over odd number sts.
N2: Tk to 1 st before marker, sl st, remove marker, sl st back, tk2tog tbl, tk to end of needle.
Rnd2: Tk1 cc (tk1 mc, tk1 cc) rep around.
Rnd3: Tp1 mc(tp1cc, tp1mc) rep around.

Rep rnds 2&3 to desired height 1-3 chevron braids.
Sewn bind off (Zimmerman).