Base rnd, each side: Multiple of 4 + 3 + corner sts.
Begin 4 sts to left of corner st.
Rnd 1: Ch 8 (counts as dc and ch-5), skip 3 sts, *[dc in next dc, ch 5, skip 3 sts] to corner st, (dc, ch 3, dc) in corner st, ch 5, skip 3 sts; rep from * around, join with slip st to 3rd ch of ch-8.
Rnd 2: Ch 3 (counts as dc), *[ch 2, sc in next ch-5 space, ch 2**, dc in next dc] to corner space, ch 5, dc in next dc; rep from * around, ending last rep at **, join with slip st to top of ch-3.
Rnd 3: Ch 5 (counts as dc and ch-2), *[sc in next sc, ch 2 **, dc in next dc, ch 2] to corner space, ch 1 more, dc in corner ch-5 space, ch 3, dc in next dc, ch 2; rep from * around, ending last rep at **, join with slip st to 3rd ch of ch-5. Fasten off.