Here's something I finished earlier in the week...a very large zip pouch made from a crewel upholstery fabric.
It turned out amazing and wasn't difficult to sew. I was a slightly concerned adding a zipper to this heavily embroidered canvas fabric would be a pain, but it ended up not being a problem. I did make sure to cut the pieces so the thick embroidered flowers didn't intersect the zipper.
To make this pouch I used this pattern piece, which is designed to be used with the Intro to Improv Zip Pouches pattern. This is quite a large pouch--notice the file folder inside--and in lighter fabrics this size pouch needs some seams for support and to help any interfacing remain adhered to the fabric.
In case you were curious, interfacing is a standard width of only 20-22" wide because it's meant to be used on smaller fabric pieces. It will start to come off if it's used on large expanses of fabric and there aren't seams or some sort of stitching to hold it down.
But if you use upholstery fabric, you can skip the seams and make a very large zipper pouch from just two pieces of fabric. Patchwork with light batting would also be perfect!