This has to be one of the most frustrating patterns that actually turned out looking normal in the end. I had to restart several times, and it took me a long time of trying to figure out which way to crochet and which size hook and how many repetitions to do. The pattern takes 19+3 stitches, which means I could do only one repetition along the 7" side, or less than two along the 9" side. However, the waves makes the pattern work up quite a bit shorter than a straight chain, so two repetitions on the 9" side worked perfectly. My only worry now is that there are large gaps that I'll have to figure out how to fill in when I stitch them together into a blanket.
I used CraftSmart Value Navy with a J hook.