There are a lot of tutorials out there with different techniques & shapes. You can even make "no sew" ones. Just google "I Spy Bag Tutorials" & you will surely find something you like. The one I linked to earlier is not one I am going to use but just wanted to show what they are. I like this one below even though I can't understand the German.
I like how she's framed the plastic.
https://www.youtube.com/watch?v=ZwLK83dGzao