I usually find a convenient spot to zip-tie the boards, if necessary.
You just need to insulate them from the case, to make sure they don't short out.
The front of the case does usually make a nice bezel though, if you are putting the monitor really close to the glass.
Just tape it to your front glass with foam tape, set the front glass against the monitor, and then mark the location that you need to mount the front glass.
I usually lay mine back away from the glass too far though, so I have to build posterboard bezels for them.