Base rnd, each side: Multiple of 6 + 5 + corner sts.
Begin 6 sts to left of corner st.
Rnd 1: Ch 1, *(sc, ch 5, sc, ch 7, sc, ch 5, sc) in same st, ch 4, skip 5 sts, [(sc, ch 5, sc, ch 7, sc, ch 5, sc) in next st, ch 4, skip 5 sts] to corner st, (sc, ch 7, sc, ch 9, sc, ch 7, sc) in corner st, ch 4, skip 5 sts; rep from *, join with slip st to first sc. Fasten off.