I made the first one out of my t-shirt from UIowa library school. As a prototype, I don't think it's half bad though it's clear that the bag is too slouchy for larger knitting projects. I used the pocket-in-a-pocket method to create a "lining" but for something this silly and casual, it seemed a little unnecessary to be so "precise". This was my first time doing any kind of sewing with knits. I cut my rectangles at 13"x17" but the size changed a lot while I was sewing and cutting.
For my second attempt I used an old Longsjo bike race t-shirt. I made sure to prepare the fabric so the Got Sisu logo is visible on the front. I also used a knit interfacing that gave the bag just enough structure to stand up to one of my larger knitting projects. Cutting my rectangle at 13"x20" helped with this too. I put the interfacing between the two fabric pieced and just sewed up the sides; I love the look of zig-zag stitching here. I am pretty sure that one of the elements of my button hole maker on my machine is broken so I had to use a snap, so the closure is kind of boring but I might go back and a button to the outside of the snap.
I am pumped to show up to my knitting group tonight with my project safe and secure in one of these bags and not hanging loose in my usual plastic shopping bag!