With a finishing Arks, Black, Translucent or the Grey that I am seeing more of, you want smooth more than flat. The smoother you can get the stone the better, finer it will polish the edge.
They are hard, so it will take more laps that we are spoiled with synthetics or waterstone naturals. Time spent prepping/lapping an Ark will give you a keen, smooth shaving edge. That edge is different than any other I have tried, hard to explain. It has a little bite, but not enough to irritate your skin. I like it.
You edge/bevel will look hazy not polished under magnification.
The burnishing of the stone face with hard steel is what refines the face for razor edge polishing.