I made these a while ago on our company's 3D printer, and I figured I'd upload the pic for anyone who's curious. I made them with a compound angle, meaning that the highest corners are where the F2 and F8 keys are, and the lowest corners are the Popup and Pause Break keys. Those actually touch the desktop, which is why the holder is split like it is.
For the very curious, the little dark spots you see on the top surface is just where the plastic from the 3D printer didn't cover completely. I must have used too thin of a wall on the top surface, but it doesn't matter, since the keyboard sits flat on the whole surface. The circle in the center is just for design, I could have just as easily made it an X shape. The little "legs" standing up around the edges hold the keyboard halves firmly in place.