Making too many increases or too many decreases will both cause the "bowl" effect. But if you are making too many increases the bowl will eventually turn into a ruffle. I suggest that you lay your piece out and flatten it the best you can and see if it appears too tight or if you in fact get a small ripple or wave. That will tell you if you need to increase or decrease more often.

If anyone wants to know I started doing 2 "knots" every other hole on the turns and it seems to be working, will decrease doubles as rug gets bigger. Also being careful not to pull too tightly.

Hi izzy. I sorta stumbled upon this board by accident, but I'm glad I did. I'm glad you figured out how to solve the problem on your rug. I like to sit at the kitchen table and work on my toothbrush rugs there. I can lay it down on the table and I can see how it's comining along as I work. If it starts to "cup" I know I need more increases. You can usually tell by the size of the stitch just below, if it's real large, you could use an icrease there. Also, if your next stitch seems too far away to the left, you could use an increase stitch.
I've made several rugs and the more I make, the better I get at it! I've made round, and heart shapes, but I love the oval ones best! Can we post pics on this board? Sure would like to see a pic of yours when you're done.

Lara...yes, you can post pics on this forum....many of us use photobucket, which is free, and a good way to warehouse your pics, too.

Yes I will post a picture when I get my son to help me. It's slow going now and not sure what size I am going to do.I bought 2 twin sheets from Goodwill still not through the first sheet and it about 18" x 24". Probably stop at about 5" more. My first one so may not be real pretty.

I finished my first one. Turned out pretty good. Have to have my son help with picture when he gets back from Spain...He went with students from his High School and 2 teachers. Yikes, didn't think I would miss him this much. Can't wait to see his next e-mail(His is a only)Started on second one. I have checked out ESTY.com to see how others use colors..Any one know how to do a square one, or is that more of the croquet method?
Found out per someones advice how to figure starting row to determine size of oval. Finished size 36" X 20". Subtract the width from length and that is the length the begining row should be. 36-20=16. First row should be 16" long then start going around and around. Picture to come in about 2 weeks I guess