Kobo Keeper

I have measured and planned my Kobo Cozy and have sketched out the rough shape of it. The outside will be a basic book jacket, but I will slip a piece of plastic sheet inside each cover to keep it stiff and protective.
The inside is more complicated and will keep the Kobo snug. Keeping tight to the outside dimension of the ereader, I drew a box and the flaps that will be attached to the back cover on three sides. The left side, next to the spine, will be loose with an extra piece that tucks behind the Kobo. I gave close examination of the rocket-scientist-engineered ones at the store and this is exactly how they do it.

Here is my sketch, including a closeup of the bottom section where I have a gap for the lonely button.