I built this flat storage camera rig to get top down shots of my desk. It's basically a large saw-horse that I attach my Joby flexible tripod to and it works great!
The plastic parts were a bit too loose of a fit for the 2x2 beams I bought at Home Depot, so you may want to scale everything down 1 or 2 percent for a tighter fit. I just used a bunch of epoxy, so that works too.
Make sure to refer to my length chart for the wood pieces for a proper fit, although you can always adjust things for your own needs! Also, watch the video for detailed assembly instructions :