Row 1: 3 double crochet in 4th stitch from hook. Skip next 3 stitches, single crochet in 4th stitch. *Chain 3. Make three 3 double crochet in that same single crochet stitch. Skip the next 3 stitches, single crochet in the next stitch. Repeat from * to the end of the row. When you have two stitches left, end with a single crochet in the last stitch.
Row 2: Chain 3 and turn. Make 3 double crochet in the final single crochet of the previous row (the same stitch as the chain 3 just made). Single crochet in the next chain 3 space (the space created between the chain 3 and 3 double crochet cluster of the previous row) *Chain 3, make 3 double crochet in that same chain 3 space. Single crochet in the next chain 3 space. Repeat from * across the row. End with a single crochet in the last chain 3 space.