1. Cut the hems off of old jeans
2. Start by rolling up one end of the hem using the fabric glue as you roll
3. Once you get to the end, apply extra glue. And let dry.
There are a couple of tutorials that say to splice pieces together with a few stitches. I didn't sew the pieces, I used fabric glue and continued to roll in the new piece. I used a large coffee mug for the size of the coaster (I wanted to make sure all my glasses and mugs could be placed on the coaster).
Here are a couple of tutorials with more detailed instructions. Take a look...
My Recycled Bags
Polka Dot Pineapple