Here is one I did with some scrap oak I had left over from my new staircase.

The base is pretty simple,just rounded the bottom on the band saw, sanded it smooth and put a fancy bevel on the edge with a router table. The center plaque is about 5" in diameter, the top 1/2 is routed (or sawed) to half thickness on the back to hold the tail. The bottom of this plaque has a "T" cut in it to hold the beard. This is the easy part, the hard part is working with the tail.
I left one row of feathers in front of the tail feathers, I have seen other mounts with several rows. I will list here the steps I used to finish the tail.
You will need a piece of board or cardboard, bondo or auto body filler, salt (1lb), pins or thumb tacks, a 1x4 4-6" long, and a brick or other weight, also a clean bench or table to work at.
1.Flesh the tail, when you have all the fat out from around the tail go back and flesh some more. This is the most time consuming part. There is a bunch of fat around the quills that is difficult to remove, try a wire brush.
2. Salt the base of the tail and beard and resalt every 12-24 hours until dry.
3. Spread out the tail on the board and tack some of the feathers into place to hold the fan like you want it when finished.
4. Side the wax paper under the quills and mix the bondo (2 1/2 to 3 tbsps should do it).
5. Work the bondo in around the quills and the little bit of skin left holding them together.
6. Fold the wax paper over the top of the quills and place the board on it, then put the brick on top of the board to smash the bondo out flat.
7. Let it dry then peel off the wax paper, presto, you have a turkey fan.
The fan on mine is held onto the base with pressure only, same with the beard. I cut the spurs off at the bone (bandsaw) and drilled them then screwed them onto the base with 1 1/4" screws. A friend of mine cuts a sillouette of the state he shot his bird in and uses it for the center plaque. Also I have seen the base of the shotshell used to hold the tail in place. Hope this is what you were looking for.