After many trials with other published sc-constructed mitered squares, none of which I enjoyed making, and none of which turned out truly “square”, all looking quite sloppy… I just about gave up with this idea. Until I tried a log cabin-esque layout, which turned out to work perfectly! And I’m using dcs for this one instead, which is MUCH faster and enjoyable.

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Note: chain-2 (“ch-2”) counts as a dc throughout.

Step 1 (see annotated picture with numbers and arrows)
First (center) color square:
Chain 13.
Row 1: Dc in 3rd ch from hook (first 2 skipped chs count as dc), dc to end (12 dcs).
Rows 2-7: Ch-2, turn, dc across (repeat until you have 7 total rows). Note that the last dc within a row will be in the top of the ch-2 from previous row.
Center color section complete.

Step 2
Switch to middle color
Dc 7 rows (as before).

Step 3
Now, pivot to start working along edge of first color:
Ch-2, put 23 more dcs evenly-spaced along edge, so there are 12 total dc on color 1, and 12 dcs on color 2 (be sure to put the last one right at the edge). (24 dcs).
Ch-2, turn, dc across (repeat until you have 7 total rows in this section along the edge). Middle color section complete.

Step 4
Switch to last (outermost) color
Dc 7 rows (as before).

Step 5
Now, pivot to start working along edge of second color:
Ch-2, put 35 more dcs evenly-spaced along edge, so there are 12 total dcs on each color (be sure to put the last one right at the edge). (36 dcs).
Ch-2, turn, dc across (repeat until you have 7 total rows in this section along the edge). Outermost color section complete.

My square measures about 10.5-10.75 inches (square). The variability could be due to the different yarn colors (HLILTY tends to be a little inconsistent), but this should be consistent enough to ease the pieces together when joining at the end. See important notes below!!

NOTE - after you get that first section (section 1) done, check to make sure it’s “square”, otherwise, this pattern would need to be modified so that your work is square. May need to adjust either the number of stitches within a row of section 1, OR, the number of rows within section 1. When you pick up stitches along the side of a particular color, you want to pick up the same number of stitches as are within a row as well (counting that first ch-2 in the total sts), so things stay square (here, I have 12 sts within a row, so I pick up 12 sts along the side as well). Also, you want to work the same number of total rows within a color as well, so things stay square (here, I’m working 7 rows within each section). In my example here, it seems that 7 rows equals 12 stitches for my gauge.

After seaming the first row of 5 squares, it measured 55” wide. After edging, I should be able to add a couple more inches to the width. Will be 5 squares wide by 7 squares high (35 squares).

I used a mattress-esque/invisible/flat stitch to seam, so it’s super flat and nearly invisible. See this project for pictures on the general idea (noting that this mitered squares afghan is much trickier for lining up the sides, as some sides are “raw” and some are more finished stitches):
https://www.ravelry.com/projects/toriellen/crazy-patchwor...

Ran out of the first skein of each green shade in the third row of squares. I don’t remember exactly how much yarn I used after I finished this - I’ll NEVER make this again, as it’s just too tedious, all of the hand-sewing joining.

Final dimensions after simple border (round 1 sc, round 2 hdc): 78”x57”

It was relatively easy to place the first round of border scs, since each small color block should have 12 stitches (36 sts for an entire square).