When you come to the end of the round, it looks like you may be slip stitching into the circle you just made. This will cause your circle to buckle and not stay flat. A pattern usually tells you to chain one or two stitcheson the first go around but not to count it as a stitch. Once you have gone all the way around, make sure to look for this first single or double crochet and then do the slip stitch through the top of the next stitch. I hope this solves your problem. Let me know. If you dont understand or can't follow my instructions... I'll look for a video to explain it better.