If you use servo's like myself it's always a trial mounting them, or creating a plate with the holes in them for fitting them in. Some time ago I saw a video that I'd recommend by Daniele Tirinnanzi. http://www.daniele-tirinnanzi.com/
In his video he showed out to make animatronic eyes.. But importantly he also showed me a product called EasyCast.
Eastcast is a 2 part fast setting resin that will set in about 10 mins. It's mixed 1:1 and is very easy work with.
Anyway - most servo's are a standard size so I rummaged through my shed and found a heavy duty plastic cutting board - about 15mm thick. This was good because the cutting board was of a non-stick plastic (the terrible ones you curse because NOTHING sticks to it)
So using my band saw I cut up a pile of templates of the standard servo sizes.
Then I rook an icecream container, although you can use other means to make the shape of the overall plate, and hot glued my templates down. This was just a trial however you can print out a nice CAD layout if you want to position the servo's.
Sorry - white container with white bricks don't photograph well. I gave this a spray with spray-able wax.
Next I mixed up a small batch of the resin and poured it. The depth of the resin will determine the thickness of your plate.
After it was set I popped it out of the container and used a small vice so I could tap the templates out. Non-stick plastic use here
Finally using a sharp knife I was able to trim any skurf around the holes and pop my servo's in.
Now - all I need to do is to drill and tap the servo holes and I am ready to test.
About 5 to 7mm of the resin is still very stoing. It's not too heavy and has a reasonable strength. It is easily workable re drilling and cutting.
Best of all - if you want to make stackable plates you can make the initial shape out of silicone and run as many plates as you want. Then stack them together. You do NOT have to use them for just servo's.. but receivers, batteries, microcontrollers.
It's all up to your imagination. Atleast I did not have to drag out the scroll saw Again.