Looking at the picture
on Ravelry, it looks like you're ok. I think that you work a section on the needles, then pick up along the edge of the next section and then proceed on to the next section of sts on the needles, etc. I can't quite tell but it looks like alternating sts on the needle with picked up sts will give you a flat edge. If maybe the sts on the needles are a row or two too long, you can decrease them.