Omitting the twists, since the pattern makes a well-fitting ribbed sock.

• 18 rounds 2x2 rib (offset to center, per pattern)
• 54 rounds 6x2 rib (again, offset).
• On second half of 55th round, begin heel flap.
• Knit slipped st heel flap until there are 16 sts in each slipped st column. turn heel per Late Night Socks pattern.
• Pick up 17 sts along each side of heel flap.
• Gusset dec every other row.
• 42 rounds with rib pattern on top of foot, followed by one round of plain knitting.
• Toe decreases per Late Night socks pattern (size medium)
• Dec every other row, ending with plain knit round and 40 sts total. Then dec every round until 24 stitches total, then kitchener.