The door was pretty simple. I measured the opening, cut 2x4s and 2x6s to the height and ripped one board to get the perfect width.

Then 4" above the top and bottom I screwed in a batten an inch narrower than the door. I made sure to get at least two screws in every board.

I divided the remaining distance between the top and bottom batten by 3 so I would have even spacing of the sections.