All sizes are worked in the same way; difference in sized is determined by needle size and gauge difference.

All size/gauges:
Small: 20 sts and 24 rows = 4” on US 7
Med: 18 sts and 22 rows = 4” on US 8
Lge: 16 sts and 21 rows = 4” on US 9

Sweater is started at neck and worked downward.