I recently made a small mantel from a piece of maple that was twisted a good 3/4" front to back. I took the slab, leveled it best I could on a job box and hot glued it down. I built a very crude router sled and planed the bottom side. Flipped it over and the top side was even easier now that it sat much flatter. I was skeptical, but it worked great. I used a 1" diameter bottom clean out bit and my average Bosch router spun it up just fine. Just make sure you go slow, overlap your router passes and don't try cutting on both the push and pull strokes. It took very little clean up with my orbital sander.
