I have a cake whose bottom tier will have diamond shaped fondant cutouts attached all over it. I want it to look clean and uniform. Does anyone know a trick on how to do this? Thanks in advance!

Steady hands and good clean diamond shapes.

If your cutouts have crisp edges and are uniform in size, your talent will do the rest.

I have also found that starting from the front of the cake and working towards the back in both directions will help if you need to overlap the last diamond.

I am a little compulsive with even spacing. I cut a strip of paper (usually just some parchament since I always have scraps) that is large enough to go around the cake. Wrap the strip around the cake and either mark or cut it so it is the exact diameter. Then fold the strip into equal size sections. Each section will then be the width that you need for the diamonds. You cut one of the sections into a diamond shape and use as a pattern. Hope this makes sense.