Step 1:
Fold your bath towels in half the long way to make two long, skinny rectangles. Stack one towel on top of the other. Place the paper towel tube at one end and roll as you would a rug. Set aside.
Step 2:
I used paper in place of fabric to illustrate this next step because the fabric edges were not clear enough to see in the photos. Fold your fabric into a tube shape so that the front side of the fabric is on the inside of the tube and the back of the fabric is on the outside of the tube. Be sure to fold your raw edges and overlap them as shown.