The design is made for glass heated beds the outside layer of the box is the one on the bottom so it will come out nice and even.
For Led light i used one of the long strips just cut some parts out and a wireless remote. I didn't want RGB colors but that will be cool.
For diffusion material you can use anything you like. I got this 8x11 papers from the art store that they use as a liner for invitations. The box is glued using super glue.