Try these instructions for the Martha Stewart oilcloth lunch bag - just adapt the measurements to suit your needs. As you can see, I didn't make all mine the same size as I was working with a limited amount of the vinyl fabric. It did take a fair amount of piecing.
The outside edge-stitching gives an amazing amount of body to these bags and they stand on their own just fine. It's really easy to grab them and toss them into the truck when they're full.
Oh, and in editing this episode, I realize there was a little thumping in the audio from time to time. I must have been tapping on the desk without realizing it - I got a new microphone that's much more sensitive than my old one, so it picks up everything! Sorry for the distraction!
I really appreciate all the comments and notes - and I will catch up eventually!