This is not your basic ribbed sock. It is based in 2x2 ribbing, with 4 panels of angled ribbing. The sock is worked toe up with a short row heel.

2 stitch markers are also needed.

Specialized stitched include make ones, both left and right, knitted and purled.

Errata
Large size, row 7 should read: P1, k2, p2, k2 x 3, p1, k1, p2, k1, p1, k2, p2 x 3, k2, p1