I started this project to use up leftover STR yarn, because the stuff is too expensive to have leftovers.

Cast on 48 stitches with the solid color over size 6 needles and knit one round. Switched to size 4 needles and did 10 rounds corrugated ribbing. Then one round knit, one round purl, one round knit with solid.

I then did alternating high and low lines.
R1: K3solid, K1STR, repeat to end of round.
R2: K1S, K1STR, repeat to end of round.
R3: K1S, K1 STR, K3solid, K1STR repeat to end of round.

Then K1 round, P1 round, K1 round. Divide stitches so 24 heel gusset stitches are on third needle. Knit back across third needle, making an M, more or less like so. No wait, purl instead of knit all the even rows, okay?:

R1: K1 solid, K2STR, K6solid, K2 STR, K2 solid, K2STR, K6solid, K2 STR, K1 solid.
R2: K1 solid, K4 STR, K2 solid, K4 STR, K2 solid, K4 STR, K2 Solid, K4 STR, K1 solid.
R3: K1 Solid, K10 STR, K2 solid, K10 STR, K1 solid
R4: K1 solid, K2 STR, K1 solid, K4 STR, K1 solid, K2STR, K2 solid, K2 STR, K1 solid, K4 STR, K1 solid, K2STR, K1 solid
R5: K1 solid, K2STR, K2solid, K4STR, K2solid, K2STR, K2 solid, K2STR, K2solid, K4STR, K2solid, K2STR, K1 solid
R6-R8: same as row 1. (Can cut STR here.)
R 6 rows in solid, turn heel using 8 center stitches, pick up side stitches, still in solid, knit across instep, pick up other side stitches, pass center and start (start STR again) alternating colors for the bottom when you hit those side stitches again. You may want to move one stitch to the instep to have a solid stitch as the first and last stitch across the instep and then K2tog on the bottom somewhere so the bottom alternates colors easily.

I can’t chart here in the notes, so I’m going to write out the box. I did two box patterns, with a row of plain in between, followed by the same alternating horizontal stripes used earlier in the sock. Do that twice, then one more row of boxes. Now start decreasing at end of every needle (SSK on right side, K2tog on left, but if all the notes above make sense to you, then you already knew that) and when you’re down to 8 stitches on top and 8 on bottom, kitchener, weave in ends, wave slipper-socks around happily, give to kid.

Obviously, if you have the experience to follow the above notes, you can probably get graph paper and figure out how to do another initial in place of the M. It’s 24 stitches across and it works best when at least the first and last stitches are solid. I did NOT slip the first stitch in each row in the second sock, which makes picking up stitches harder but gave me less trouble with holes along that single solid stitch.