Cast on 68 stitches and work 1 inch in twisted rib.

Work six inches then divide for heel. Heel flap = 18 purl ridges (36 rows) in slip-stitch. (I didn’t bother with the garter stitch borders.)

Turn heel: slip 1, k19, ssk, k1, turn; slip 1, p7, p2tog, p1 turn; etc.

I don’t know why, but for some reason I was convinced I’d only cast on 64 stitches for these socks, so the heel is worked over 32 stitches and I decreased the gussets to 32 stitches (16 on each needle). Of course I then needed to decrease an extra four stitches from the foot stitches when doing the toe. The result is actually a really nice fit across the foot, so even though it wasn’t intentional this time, I might do it again.

(Colour is very accurate in top photo.)