Double chain, step 1.Begin with a slip st, then chain 1. Insert the hook into the bump on the back of the chain just made and pull up a loop.
Double chain, step 2.Yarn over and pull through both loops on hook.
Base rnd, each side: Multiple of 4 + 3 + corner sts.
Begin 6 sts to left of corner st.
Rnd 1: Ch 1, sc in same st, *skip 3 sts, 3 dch, sc in next sc; rep from * around, ending last rep skip 3 sts, join with dch join in first sc.
Rnds 2 and 3: Ch 1, sc in dch-space just formed, *3 dch, [sc in next dch-space, 3 dch] to corner space, (sc, 3 dch, sc) in corner space; rep from * around, dch join in first sc.
Rnd 4: Ch 1, sc in dch-space just formed, (3 dch, sc) in same space, 1 dch, *(sc, 3 dch, sc) in next ch-space, 1 dch; rep from * around, join with slip st to first sc. Fasten off.