What most naturally follows?

How to cut slate
Flip the slate over when manually cutting the slate.
It's much easier to draw and cut a straight line across the bottom side of the slate. When cutting slate manually with a hammer and chisel or a handheld slate cutter, flip it over and cut along the flat underside of the tiles.
Mark and cut the top of the slate when using power tools. When using power tools, it's more important that the slate lies flat on the surface you're cutting on.