20 sts + 14 rows = 4' in sc.
Be sure to check gauge.
Row 1: Sc in 2nd ch from hook and each ch across – 37 sts.
Row 2: Ch 1, turn. Sc in each st across.
Rep Row 2 until piece measures about 10' from beg.
Next Row: Ch 3 (counts as 1st dc), sk next sc, work 1 dc in next sc, * skip 4 sc, (dc, ch 1, dc, ch 1, dc, ch 1, dc) in next st – Shell made; rep from * across, end last rep skip 4 sc, 2 dc in last sc.
Next Row: Ch 3, turn. Skip next dc, dc in next dc, *work Shell in center ch-1 space of Shell; rep from * across, end 2 dc in last dc.
Rep last row until piece measures about 13' from beg. Fasten off.
Fold lower edge of bag up about 5' and seam sides. Sew on button. Use space between sts for buttonhole. Weave in ends.
beg = begin(ning)
ch = chain
dc = double crochet
rep = repeat
sc = single crochet
st(s) = stitch(es)