Work a chain of 90 stitches, work 89 single crochet on chain, now work
24 rows of single crochet, always taking up the back loop of the
preceding row, on the next row work 19 single crochet, chain 12
stitches, skip 12 stitches, work 1 single crochet in each of the
remaining stitches. Work 24 rows more. Join with slip stitch.