Cast-on 64 sts.
K1, P1 rib with back-to-front (eastern?) stitch mount, for 14 rounds or 1.25”.
Switch to front-to-back stitch mount, as per usual, for ensuing stockinette.

Work straight until 4.25” from cast on edge.

Heel Flap: 31 sts
RS row: sl1 kwise, k1, sl1 pwise, k1 rep to last st, k1.
WS row: sl1 pwise tbl, p to end.
Total rows = 36, 18 selvedge stitches to pick up on either side.
Heel: 12, 7, 12
In-step: Dec. every 3rd round 5x, then every 2nd round until 64 stitch total again.
Foot: stockinette straight until 6” from heel flap pick up edge.
Toe: Dec every 2nd round, 6x, then every round until 6x2 sts remain. Graft toe.