I 'made' a very modular laptop table out of the following:
- a wire desk basket (or is it supposed to be a magazine rack?) that's about 15" by 12" by 4" (with the lowest part of the tray itself being about 1" higher than the bottom of the 'legs')
- a 1" thick foam "paddle board" (like a kid might use in a swimming pool) that's just large enough for the metal basket to sit on top of it
- the foam-padded laptop carrying case that I keep the MacBook in when I'm travelling. I put this under the laptop in side the wire basket, so the metal of the tray doesn't damage the computer or the cords, flash drives, etc. plugged into it.

The curvature of the wire basket tray keeps the laptop case from being flush against the computer, thus allowing a lot of its heat to dissipate. With the foam paddle board under the wire basket, my lap is about 4 inches removed from the laptop and somewhat insulated, to boot.

All the parts of this "laptop desk" are separate and not physically attached to each other, so it's easy to use each of them for some other purpose (e.g., as a pool flotation device, a laptop case, and a wire desk basket) if/when the need arises.