There is this problem where working across the board squares, you get what I call the zaggies.
If you work along the lines your cutting will be fine, it's just a matter of timing and position.
If you desperately need your cutting where it is try using embankment splines along the sides that will hide the corners of the squares where the ground level has been raised. There are quite a few on the DS, grass, earth and made-made materials.