We have shown one-off custom versions of this that cost thousands, yet here is a simple fold-down desk that you can carry anywhere. Jai at Cool Tools says "I use this portable desk as a stationary desk at work and love it. If you need to relocate your workspace for whatever reason, it folds into a large portfolio style case with handles, so it's quite easy to move your 'hub' with you. You have to provide two pieces of plywood, which slip into two pockets to create the rigid surfaces. Installation is a snap: two metal "O" rings on either edge allow for easy hooking on any sturdy screw/nail/hook."
"The rings are 48" apart so they line up with any standard 16" O.C. wall stud system. I've been using it for a little over a year now. Boy is it sturdy. The case is nylon with nylon bands well-stitched to support all stress points. The ability to adjust the height is key, as I prefer to use a stool rather than a chair at my work. The working distance from the floor to my desk is approximately 36", so it's more like a workbench, except with this desk, there are no legs to deal with." ::Cool Tools and ::Amazon