Base rnd, each side: Any multiple.
Begin in any stitch.
Rnd 1: Ch 3 (counts as dc), dc in each st around, placing 3 dc in each corner st — corner group made, join with slip st to top of ch-3, slip st in space between first 2 sts.
Rnd 2: Ch 3 (counts as dc), *dc between each dc to corner group, (2 dc between dcs of corner group) two times — corner group made; rep from * around, join with slip st to top of ch-3, slip st in space between first 2 sts.
Rnd 3: Ch 3 (counts as dc), dc between each dc around, placing 3 dc between 2 dcs in center of corner group; join with slip st to top of ch-3.
Rnd 4: Ch 1, sc in same st, ch 3, *sc in next st, ch 3; rep from * around, join with slip st to top of ch-3. Fasten off.