Well, I can only hope to help some collectors along the way... Today I saw an older collector and even though he's in the nursing home he is always willing to help and has a head full of knowledge...I can hope that one day I'll be able to do the same. Take a hack saw and go around all four sides and then just pop it off--NOTE..I have never cracked open a slab, but this is the way I've heard of. Speedy
A simple hammer will crack that nasty ol slab, simply beat on the side of the slab evenly and it will crack, works everytime! You may want to wear eye protection in case some material flies upward...
Assuming you were serious about the c-clamp in the first place.... Do you place the c-clamp against the slab's edges, and turn the screw? Or do you place it on the slab's front and back faces, and turn the screw?