Simple saddle bag...
 

Built this for my e-bike, tried to keep it pretty easy. Biggest hassle was the edges, as I had to pull the needle and waxed thread through each punched hole with a pliers...hundreds of times!

https://cimg8.ibsrv.net/gimg/bikefor...464264b8f4.jpg
https://cimg9.ibsrv.net/gimg/bikefor...de50cc5ec1.jpg
https://cimg8.ibsrv.net/gimg/bikefor...3d64701737.jpg