As far as tooling for this project, here is a pretty good idea of what you'll need:
Heat gun (hairdryer will work)
First, purchase a sheet of 4ft x 8ft x 3/4 inch plywood. I used the flooring grade as it will be covered later.
Cut the sheet into 8 2ft x 2ft squares and mark their center points by drawing an X across the middle from the corners. Drill a 1/4 inch hole in the middle of them.
Using a router table, measure out 9 inches from the edge of the cutting bit and bolt your wood square loosely to it. Turn the router on and plunge it slowly upwards until it goes through the wood. Lock the router in place and proceed to rotate the squares until you complete the circle. Repeat eight times. This will give you 18 inch circles. Why 18 inches? I am using an off-the-shelf plastic dome that is that size. Specifically, it is a clear dome from Aspects
used for bird feeders. This was purchased from a bird store for $35. The shot dispenser we are using is available on ebay
new for $30.
Three of the circles will be cut into rings. To cut out the centers, I made a quick jig as pictured to be able to rotate the circles against it. Two of the finished rings should be 1.75 inches thick and one will be 1 inch thick.
Take one of the circles and setup the router to create a groove about 3/4 through the thickness for the dome to sit in.