The felt with adhesive backing works well. You can get it in thicker form by finding door and window insulation strips at a local lumber yard or building supply.
My word of caution concerns "flocking", used to line jewelry boxes or special drawers normally. I used it several years ago for a fancy gun cabinet on both the base plate and the rack. It forms a felt like covering and leaves no seams or lumps. Looks terrific. The downside is it will quickly affect blueing. I nearly ruined an expensive double before discovering the problem. Contact with the distributor and manufacturer for answers led nowhere. Caveat emptor.
