If you use lexan you can do an almost invisible install by driving some flat head screws into the wall at the corners and midpoints---measure carefully. Glue tiny (1/16 or 1/8" D) super magnets to the back of the lexan to match up with the screw heads---again measure carefully. Stack them to the desired thickness. Fit the panel in place.
This might work for glass too but it is heavier. You might have to drill it and using a nylon spacer and screw anchors.