Not in my slow cooker...
from left to right (best guess): black bear, cougar, cougar, bear cub, lynx, badger. On the bottom: polar bear. Conversation the other day turned macabre as guests, who are heading out bear hunting this week, asked my husband how to clean a bear’s skull for display - not surprisingly, my husband knows about these sorts of things.
Mammal’s skulls tend to hold together much better than the skulls of reptiles or birds, so preparing them is simpler. First remove the fleshy bits as close to the skull as possible. A sharp knife would do the trick.
Get rid of the eyeballs (perhaps give them to a friend for a tasty treat, in Mary Roach’s Gulp she mentions cultures who enjoy that sort of thing). I’m not sure exactly how one removes eyeballs from a skull and I really don’t want to be spending time thinking about it - no doubt I will at 2am.
Someone would have to commit the zombie act of removing the brains. A chopstick stuck inside and swished about would work. Once the brain is pureed, shake it out.
Now it's time to get all CSI and slowly boil the skull. A slow-cooker would be ideal. Cover the skull with water, turn it on low and walk away. After a very long time, a day or so, the remaining flesh and tendons would fall right off (like any well done rack of ribs). You could baste the beary-soup with a solvent like alcohol or acetone to remove excess oils out of the bone. Pull the skull out and set it aside to dry. Fish any teeth that fell out from the resulting broth, dry them off and use white glue to put them back in place.
For a final touch, spray a 10 percent solution of white glue over the entire dry skull. This prevents the bone from drying out and delaminating (powdering), incidentally, this is the same technique used to set fake turf onto a super-detailed model railway - in case multitasking of model railways and skull preparation ever comes up. Keep bleach and peroxide away from the skull as both act to break down proteins in the bone causing it to turn to powder far sooner.
All that is left is to find a nice place to display the skull. If you ever want a skull but don’t want to put in the work, nice replicas can be found (e.g. here).
As a tangent - the conversation was entirely hypothetical as the would-be-bear-hunter had no plans on taking a rifle into the woods with him.
Case of skulls photo was taken here