Commercially available AV wallplates don't always blend in with standard wallplates, and sometimes you simply can't get off the shelf wallplates with some types of RF connectors.
This is how I use blank wallplates which match my existing wallplates to make custom AV, radio and whatever wallplates.
First of all, decide where to put the connectors. This will depend on connector size, wallplate size, wallplate curvature, ease of connector use if closely spaced, and loss of strength if you swiss cheese the plate too much, and of course, aesthetics.
In this case, two N connectors will be mounted, with their centres spaced 13 mm from the centreline. A set of calipers is used to score the plastic. The wallplate has centrelines already moulded in.
Having done this, carefully drill pilot holes centred on the marks.
Then mount your connectors
Then prepare your cabling for the connectors and mount the wallplate.
Then use it! This wall plate brings the quad band antenna to the FM8900.