Sorry, I got tied up with some stuff last night. I have a very busy weekend coming up. Essentially, my background was made with great stuff type foam (I use ge foam from Walmart), covered with titebond 3 wood glue and a mix of sand, cocofiber and peat moss that I made up. I would not use the peat moss though, just stick with straight cocofiber.

A trap door is easy. Cut a hole in your false bottom big enough to give you access, then cut a piece of egg crate larger than the hole. Lay the larger piece over the hole, cover in screen and you now have an access door. Yes, you'll have to pull the substrate to access it, but that is so much easier than tearing the tank apart to get to the filter.