One additional comment here
I basically use this method all the time for my "ground brushes". Check DF or NT for example and you'll see the pattern. Usually I want the ground to be a little uneven so that it looks more realistic. Additionally, we need additional brushes for blending so it is good practice to create a template like this
ASCII Art to be replaced once I have my stuff up and running again
And modify the vertices as described by Red.
Here is the comment:
However, you HAVE TO use triangular brushes, even if it means a little more work on the template. If you use squares or rectangles you are heading for trouble (sparklies, broken brushes).