I made it a long time ago but keep forgetting to post the details. First the materials used were:
a cheap piece of 2'x2' plywood for the base
rabbit fencing for gardens
pre-cut boards for the runners(Which was a mistake)
I had my wife stain and paint the runners as well as put in the carpeting. Originally tried to use carpet tacks but they kept coming out of the plywood too easily, ended up using a staple gun with wood staples which worked perfectly(You can't see them in their or anything, and pretty sturdy). Construction was simply drilling guide holes for the wood screws, I just made marking for the runners to baseboard, but should have made a jig, even though that went okay. One thing is that the plywood was only 3/4" thick so my slightly unstraight holes were a problem since they bowed the wood. I need to make a jig sometime just for doing straight down holes. I was thinking of maybe taking 3 boards attached to a block with a drill hole in it, the boards would stick up and act as a guide for the drill body, and to use it you could just keep it flush against the back and work it down through the hole. One good idea that came from this was attaching the fencing to the baseboard with staples first and then sandwiching it with the runner using woodscrews. It makes it seem very solid and I can't imagine the fencing coming off, even though the baseboard is crap wood. Another problem was the pre-cut boards, they aren't precise and left a small gap...I now own a decent hand saw(For $7) that I use which would have been perfect. The door isn't attached since when it's not in use as a travel cage we cover it with an old yoga mat so it provides a hiding spot and a place to climb. I will probably attach the door with just some cable ties and maybe 'lock' it with velcro(Since during travel my rabbit doesn't attempt escape), so I can take off the door easy later on.
The pics, although not the best since they were taken as an afterthought: