This was such a quick and easy project. I simply cut out two rectangles of fabric per bag. The bags that I used have straps that are attached on the outer layer which leaves a nice area for attaching a panel of fabric. The size of the area I was covering was 7"x13". I cut my fabric to 8"x14" and turned in all of the edges 1/2". I pressed the fabric and pinned it into position on my reusable bag. The only thing left to do was sew...so that's what I did. You just need to take care not to stitch through any of the other layers of fabric as you feed the bulk of the back through your machine. You could easily dress your bags up even more by adding ribbon, trim, flowers, or an applique. I thought that I'd leave mine as simple as possible so that my husband might still be willing to carry them when he runs to the store.
I'm pretty pleased with my dressed up reusable bags. Let me know what ideas you have for dressing up your bags.