When i had alot of hash, or my borther did, we stuck it in the microwave for like to 10 secs, while heating a knife up under the grill of our cooker, waitied untill it was hot took hash outta microwave (usually about 6 or 7 secs) then cut though with a hot knife, using a towel not to burn our hands pushing down on it.

Or just put it in a thick bag, and smash it agaisnt a wall. Works fine... aslong as the bag dont split.