I tried to do this one time and had some success. What I did was take an old bass worm and cut out a piece of it that was about the size I wanted my body to be. I then fit it on a jighead the size I wanted to use. Super glue it to the head. Then make a form out of aluminum foil about 1/2" deep 2" by 3". Mix up plaster of paris and fill the form with it. After a few minutes when the plaster starts to firm up set the jighead in the plaster with the eye up and about 2/3 to 3/4 of the jig & body in the plaster and let it set up. After it sets up remove the jighead and rubber and using an exacto knife trip up any spots you think need adjusted. You will need to cut a spot for the feather to lay in but don't cut it to big or you will have plastic spilling out on to your feathers.
I hope this makes sense.