After I got home I decided to press on with Frame Bag #2. Taking what I learned from making Frame Bag #1, I showed and told my neighbor what I was doing and asked her for advice. She was quick to notice the mistakes I made and told me how to avoid them.
I patiently made my way through #2 and I was pretty happy with the result.
#2 and #1.
The corners are actually corner like
so the bag has the desired box look.
And it looks great on the NFE.