To keep a sharpening stone as even as possible it's best to

A sharpening stone will perform best when it's flat, and there are a couple of different techniques used to keep that even surface. The easiest method is to apply some 100 grit sandpaper to 1/2" of glass with some adhesive, then run your stone over the sandpaper it until it's flat.

Explanation:

keep it flat, run your blade evenly against it, make sure you run the blade away from you