I decided the easiest way to make the bag taller (rather than redoing the entire trapezoid shape to make it longer/larger) would be to add a single strip of fabric in the width I want the bag to be to the bottom. This is also the fabric that I'll be using to bind the bag and make the straps. I probably took a picture of it in the worst spot because it isn't really apparent that the colors do actually coordinate.
The next step is to layer it over top of some canvas and a couple layers of batting and quilt it. Then I have to cut about a MILLION little slits in the edges so that it frays nicely, wash it and I can finally begin the parts that make it take the shape of an actual bag. I love that part! I love seeing something come together and seeing if it looks how I envisioned it.