I started to work on a Reign in Hell board. I had a wood border cut to size (22 x 30 inches) in the local DIY market. First I glued the four pieces, using a lego block to get 90° angles.
Not the two squares that will support the bottom MDF sheet in the middle.
Then I glued in a sheet of 3mm MDF as the bottom layer.
I had the sheet cut deliberately a bit smaller than the inside area should be, to avoid having the floor too large and preventing the the wood borders to connect at the edges. The gap I filled with wood filler.
The cutting wasn't done like I imagined it, and I also had to fill the edges.
To do that, I glued tape on the inside, and used the same wood filler again as to hide the gap of the bottom board.
