On my cabinet, which is 27" wide, I cut the bezel and Plexi to be 27 5/8" wide. I then cut a 3/8" deep slot in each side panel on my cabinet using a router and straight edge. The bezel and plexi are inserted into the slots. My slot is a little wider than the thickness of the bezel/plexi combo, so I have some 2x2 scrap screwed to the sides (behind the bezel) to hold the bezel/plexi tight to the front of the slot.
No fasteners visible!