After trying a junky laptop stand sold in bed bath and beyond, I tried to make my own out of an old Ikea table (price: about $15). Basically you attach one set of legs as suggested by Ikea, and and then nail the other legs at right angles. You'll need to glue some kind of ledge for the laptop to rest against. I used crafter's Popsicle sticks.
The result was stable and exactly to my designed dimensions, but very hard to adjust. I would recommend mocking up the product by first using duct tape, and then using nails to affix the legs once you have the designed tuned to your needs. Keep in mind to mock up on a bed surface, because the legs will sink in a bit, making the whole thing a bit lower to the ground.
In the end I think I made it a bit too low/steep. Even so, I found it hurt my neck look at the laptop, so I gave up on it eventually. If you don't need to lay absolutely flat, this kind of stand would be much more likely to work out for you. I conclude that the laptop in bed stand, DIY or not, isn't for me. If you are OK propped up on pillows a bit, though, you might consider it.
