Front & Back (make the same):
Loosely cast on 72 (80, 88, 96) sts with larger needles. Work in garter st, slipping the first st of every row until total length measures 10”, ending with a WS row. Continue in garter st, increasing 1 st at beginning of every row as follows: (Slip 1, Kfb, knit to end of row) until there are 100 (108, 116, 124) sts. Continue even if necessary until total length is 14”, ending with a WS row. Place safety pins or removable markers at side edges to mark armholes.
Continue even until total length is 21 (21, 22, 22)”, ending with a WS row.
Shoulder shaping: Bind off 5 sts at beginning of next 10 rows. Bind off 3 (5, 4, 5) sts at the beginning of the next 4 (4, 6, 6) rows. Bind off remaining 38 (38, 42, 44) sts very loosely. Use the largest needle if necessary.
Sew up shoulder seams, leaving center (final bind off) open for neckline.
With smaller needle, pick up and knit 58 (58, 66, 66) sts around armhole. Knit 4 rows. Bind off loosely.
Sew up side seams to armhole markers. Sew up armhole band seams.
Option: Bottom 4” can be left open at each side edge for side vents.