Errata:
Turn Heel:
Row 1 should be: S1, K18, SSK, K1, turn.

This sock is worked from the cuff down. The pattern looks far more complicated than it is to knit and because the pattern is not stretchy, the cast on number of stitches is more than is usual for a ladies size medium. If you do need to make it smaller you can subtract increments of 8 stitches and then adjust the number of stitches in the heel flap and instep.