I had some remnant canvas (I think it's meant to make outdoor cushions) hanging around, and I saw this idea in a magazine (either Country Woman or Country Living). This is my adaptation:
I painted the fabric with chalk paint (Martha Stewart), then folded up the top and bottom. Instead of futzing around with mitering, I just used some pretty duct tape on the sides. I also used the tape to attach the ribbon tie. Here it is rolled up:
Something easy and cute for a kid to take to a restaurant or use on a road trip!