Pattern notes. This pattern assumes familiarity with sock knitting.

Original prototype Size 41 with high instep

Eyelet rib in the round: 
Round 1: (p1, k2tog, yo, k1 yo, ssk) 
Rounds 2-4: p1, k5 
Round 6: (k1, yo, ssk, p1, k2tog, yo) 
Rounds 7-8: k3, p1, k2

Cast on 84sts in tubular cast on in main colour.

Knit 1.5 inches in k1b, p1 rib

Work 9 repeats of eyelet rib pattern

Heel flap:
Join contrast yarn. Heel flap = 3 stitches garter stitch on either side, and work heel in Eye of Partridge until 22 ridges of garter stitch are done. (20 ridges for a regular height instep)

Turn heel from 8 centre stitches using k2tog and ssk joins on short rows.

Beginning of round – Work 43 stitches in eyelet rib starting with round 1. 
Gusset decreases – K2, K2tog, K to last 4 sts, ssk, k2. 
Continue decreases until 41sts remain on sole of foot.

Work instep in eyelet rib across top 43 stitches and stockinette across 41 sole stitches until 2.5 inches from picked up instep row

Work instep in eyelet rib, k2sts, work to last 2 sts in p1-k1 rib, k2.

Continue with instep in eyelet rib as established and sole in 1×1 rib for 2.5 inches.

Work instep in eyelet rib and sole in stockinette for 1.5 inches. Redistribute stitches so there are 42 instep and 42 sole stitches.

Change to contrast colour and work 2 rounds.

Work standard toe decreases until 16st remain (8 instep and 8 sole).

Graft toe stitches and weave in all ends.