I agree with the heat, but in lieu of invading the kitchen, a MonoKote iron can get it done, too.
I was working on a "frozen" engine last month.
It defied WD-40, denatured alchohol, and acetone, but came loose to the heat gun.
ps: The crock pot is good for surface oil, but I wouldn't bet on it (or wait all night) for a frozen engine.