The tutorial I read said to sew all the strips together but they were too thick and actually clogged up my sewing machine! I used clear tape instead and that worked just fine to hold them together. Then, I used mod-podge on one side, let it dry, then did the same to the other side. After it was completely dry and the strips were secured to one another I sprayed each side with a clear, water-resistant spray, let dry, and they were done!
I used 11 strips per place mat but you could certainly use more and I kind of suggest it because although mine fit a plate, its more of a tight squeeze :P