Open the glue joins with a craft knife and layout it out flat. Move it to a well-ventilated area and spray the outside with glue. I like 3M Super 77, but any permanent spray glue will work.
Place the glue side down onto the fabric. If the fabric has a right side and wrong side but sure the glued side of the box is on the WRONG side of the fabric. The Houndstooth doesn't have a RS or WS or it doesn't matter.
Using either tacky fabric glue or low temp hot glue carefully turn all the edges of the fabric to the inside of the bag. If you are using tacky glue be patient while the glue dries. You will have to keep pressing it down until it dries enough to grab.
When you have glued down all the edges re-fold all the creases in the bag so you can see them clearly.
Outside of the covered bag.
Refold so the shape is neat and the creases are flat.
Now cut out some lining fabric. I used a lovely crisp silk in a medium gray. Don't worry if it is thin since we will line it.
You will need a piece of paper slightly larger than the bag to laminate to the lining. Spray the paper with glue and attach the lining fabric.
Since the lining will need to be smaller than the bag, draw another line slightly inside the outline of the bag and cut on this inside line.
You will now have a lining and outside that are the same shape, with the lining slightly smaller than the outside.
Now glue the paper side of the lining to the inside of the bag. Use a roller to get all the surfaced attached.
To finish this I added a couple of grommets on the two ends for a strap. A bit of velcro to close it and a button for fun was all that was left.