I just recently donated my body "to science" (actually to a medical school). They specifically asked if keeping skeletal parts was a-ok or not as part of the authorization form signed. They also asked if stabbing, burning, or blunt force trauma was ok. I told them they could do whatever the heck they wanted, just not to waste anything. If that includes selling parts to make money for the school, cool by me. The best part of the deal is zero funeral expenses, and they'll even give your family back the cremated ashes for free. Though as part of the additional 'ok to skeletonize' part I signed, no remains would come back to the family.
The most common ways to remove flesh from the skeleton avoiding bone degradation as much as possible are maceration (bacterial, enzymatic), or flesh-decomposing bacteria (edit: and beetles). There's not much left for cremation. Mechanically defleshing the bones would be a bit more destructive, still not leave clean bones, and at the very least would be gruesome for the cleanup crew.
