To start, I scaled up my drawing and laid it out on a piece of hard foam.
Then I traced the shape out onto the foam board using a marker.
Next I used my hot wire tools to cut the foam away. This stuff is toxic so I was careful to work in the garage and wear a mask!
Once everything was cut out, I drew in some guidelines for the shapes and began carving away using a serrated knife.
When I had the basic forms started, I refined them using files, rasps and sandpaper to further define the medallion.
Finally I put on a coat of primer to seal it. This serves two purposes: to keep the crumbly bits out of the clay and to give an even 'tooth' for the clay to adhere.
I'll let this dry overnight and then I'll come back with some warm oil-based clay and begin sculpting over this armature foam.