Base rnd, each side: Multiple of 2 + 1 + corner sts.
Begin in any stitch.
Rnd 1: Ch 3 (counts as dc), dc in each st around, placing 5 dc in each corner st, join with slip st to top of ch-3. Drop loop from hook and place st on holder.
Rnd 2: Holding work so that base rnd is on the right, join new yarn around post of ch-3 from previous rnd, ch 1, sc around ch-3; *rotate piece so that base rnd is on the left, 3 dc around post of next dc**; rotate piece so that base rnd is on the right, sc around post of next dc; rep from * around, ending last rep at **, join with slip st to first sc. Fasten off.
Rnd 3: Place dropped st back onto hook, ch 1, working into dcs from Rnd 1, sc in each dc around, placing 3 sc in each corner st, join with slip st to first sc.
Rnd 4: Ch 3 (counts as dc), dc in each st around, placing 5 dc in each corner st, join with slip st to top of ch-3. Fasten off.
Rnd 5: Rep Rnd 2. Fasten off.