Here is a video of how to make the bags. Much easier to watch it done. I went one step more. I ironed fabric to freezer paper and folded. I have a great looking custom bag for pennies. Have you seen the cost of fabric gift bags?!!! I stitched around the top so the freezer paper wouldn't come loose. I used fabric glue for the bottom or I could have fused it. Start with printer paper first, it's stiff and holds a crease so it's easier to learn how to do it. I can make a catalog page bag in 2 min. I use tape not glue, it's faster and holds better. Oh, I used decorative edge scrapbook scissors to add interest to the top of the paper bags. It's addictive.
http://www.youtube.com/watch?v=Oi9JMg6vRf4