Base rnd, each side: Multiple of 5 + 4 + corner sts.
Begin 3 sts to left of corner st.
Rnds 1 and 2: Ch 1, sc in each sc around, placing 3 sc in each corner st, join with slip st to first sc.
Rnd 3: Ch 4, Partial tr in same st, *skip 3 scs, [2 Partial tr in next sc, yarn over and pull through all 4 loops on hook, ch 5**, 2 Partial tr in next st, skip 3 sc] to corner st, 2 Partial tr in corner st, yarn over and pull through all 5 loops on hook, ch 7, 2 Partial tr in corner st; rep from * around, ending last rep at **, join with slip st to first cluster, slip st in next ch-5 space.
Rnd 4: Ch 1, *(4 sc, Picot-3, 4 sc) in each ch-5 space to corner space, [5 sc, Picot-3, (ch 3, slip st in same ch) two times, 5 sc] in corner ch-7 space; rep from * around, ending last rep (4 sc, Picot-3, 4 sc) in final ch-5 space. Fasten off.