First off, I tried to make it up quickly before I went on our RV trip. I had a few hours and really, it could have been completed if things had gone smoothly.
But things never go smoothly.
It melted the interfacing on to the fabric.
After buying more interfacing, recutting fabric and interfacing, and turning down the iron, I tried again. It stuck, barely, and was a time-consuming chore.
Then I sewed up the outside and flipped it. Seams broke in a few places because I didn't think ahead and used the recommended 1/4" seam allowance, which is pretty stupid on a bag.
Finally, with the interfacing delaminating in places, the seams poking through in others, I managed to sew the corners together wrong. That's when I gave up.
When I got back from vacation, I tried again. I had cut out extra of some pieces and had interfacing on some. Otherwise, I would have chosen something else for the outside pocket.
This time I used 1/2" seams, trimmed every piece after putting interfacing on or sewing pieces together, and sewed the corners properly.
It's a little garish—I used excess quilting cotton in my stash—but I think I can use it. Maybe. Maybe I'll make another one in some other remnants I have.