Just thought I'd share. This wasn't my first foray into "upholstery," such as this is, but it's definitely my first attempt to modify a car interior in any meaningful way.

Sorry, but the pictures are terrible. It's mainly 5/8" LDF/particle board, with a piece of 2x2" cedar at the front (where the hinges are mounted) and industrial packing felt tacked to the underside and doubled up for rolled edges. The carpeting is what Canadian Tire had on hand. I glued it all down with 3M spray adhesive, and it all sat flush until the first time it got hot. Now my rolled edges are gone! I'm going to pull it out and stretch and tack the underside with upholstery tacks to get it all to sit a little tighter. It's hinged with fairly basic hardware (covered in heat-shrink tubing) to the factory hinges, or whatever those things are.

It was pretty much a fly-by-night, very hungover operation. If anyone wants some measurements to attempt their own, please let me know!