Hey guys, meant to take some photos while building this and forgot, but I figured I'd post this to give some inspiration. Box is .7 cubic feet (minimum .6 with this woofer). 3/4 inch medium density fibreboard. Fit without cutting anything behind it. Lost the OEM Nav, but for N. America cars, that isn't a loss at all. Amp is hidden in the spare tire well/tool kit. 10 inch woofer BTW, a 12 inch won't work in this location.
Because I couldn't source a matching carpet, I recovered this and the battery hatch door with as close a material as I could find. I'll be doing the trunk in Alcantara soon anyway, so this material works for now (same texture/pile, just a bit darker, maybe half a shade, looks much worse in the photos than in person). Here are a few photos. If you have any questions on building a similar one I'm here to help