Base rnd, each side: Multiple of 8 + 1 + corner sts.
Begin 1 st to left of corner st.
Rnd 1: Ch 6 (counts as dc and ch-3), *[skip 3 sts, dc2tog in next st, ch 3, skip 3 sts, dc in next st, ch 3] to corner st, dc2tog in corner st, ch 3**, dc in next dc, ch 3; rep from * around, ending last rep at **, join with slip st to 3rd ch of ch-6.
Rnd 2: Ch 5 (counts as dc and ch-2), *[(dc2tog, ch 3, dc2tog) in next cluster, ch 2, dc in next dc, ch 2] to corner cluster, (dc2tog, ch 5, dc2tog) in corner cluster — corner group made, ch 2**, dc in next dc, ch 2; rep from * around, ending last rep at **, join with slip st to 3rd ch of ch-5.
Rnd 3: Ch 1, sc in same st, ch 5, *[sc in ch-3 space between next two clusters, ch 5, sc in next dc, ch 5] to corner group, (sc, ch 5, sc) in corner ch-space, ch 5**, sc in next dc, ch 5; rep from * around, ending last rep at **, join with slip st to first sc. Fasten off.