There are loads of downloadable patterns online and great patterns available from Simplicity, Butterick and the other mainstays. I don't need to include those. I usually start with one of those patterns but end up adapting them to my own taste.
What I want to do with this page is post some of my adaptations in case you find them helpful, too. In general, I don't like cutting around a pattern so my patterns will have dimensions you can use to cut your fabric on a cutting board. One big advantage of sewing bags is that the pieces are usually square!
Here's the first pattern. It's a standard pillow case shopping bag pattern to which I've added top stitching on the edges. It takes a few more minutes but it creates a nice paper-bag type shape that is easy to load. See what you think and let me know if you think it's worth the extra time!
BTW, I know its too small to read. Please download and view or print.