Our minimum filler width is 2”. You can certainly trim that down a bit if you want, but 2” is our standard as anything smaller can cause issues with drawing the eye to an odd seam in between the walls and the cabinets. Imagine is you have a 3/4” wide filler that has to be trimmed to 1/2” at the bottom and 1.25” at the top. It draws the eye and showcases the poorly constructed out of plumb wall. With a wider filler this is not so noticeable.