At the bottom end of the bag, take the flap that points up to the top and fold it back to the bottom. This gives you a double thick spine.
Secure the spine with any of the following options:
- stapling through the bottoms of the bags
- punching holes and securing with ribbons, fibers, eyelets or brads
- sewing through the bottoms of the bags
Embellish to your heart's content.