Base rnd, each side: Any multiple.
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.
Rnd 2: Ch 4 (doesn’t count as a st), BPtr in each dc around, placing (ch 2, BPtr, ch 2) in corner st — corner group made, join with slip st to top of first BPtr.
Rnd 3: Ch 4 (doesn’t count as a st), *BPtr in each tr to corner group, 3 dc in next ch-sp, BPtr in corner st, 3 dc in next ch-sp; rep from * around, ending BPtr in each tr to beg, join with slip st to top of first BPtr. Fasten off.