To cover the interior I used posterboard cut to size. It is flexible enough to work with and stiff enough to hold its shape. I save all kinds of things that might be re-usable in crafting. A piece of shirt board could work if it is of sufficient size. Run glue down the two long edges, smooth the fabric neatly onto the glue. Make hospital corners to finish the two short sides. This will be turned pretty side out and slipped into the canister. I don't glue mine in. If you choose to use glue to secure it, DO NOT DO IT YET! The bottom needs to be finished first. You can just set the liner aside at this point.