Using a sharp knife, carefully remove the bones from the thighs.
Sprinkle the insides with kosher salt and pepper to taste. Lay 2 (or more if you like) sage leaves and a few rosemary leaves inside.
Roll up the thighs and, if necessary, truss the thighs together. I’ve never had to do this, and they come out just fine. Sprinkle with salt and pepper. Cover and refrigerate until 30 minutes before cooking time.
To a stock pot, add 3 tbsp of olive oil, several leaves of fresh sage, and a sprig of rosemary. Heat over medium heat and add the bones.
Continue browning, turning every few minutes until crispy and brown.
Add the garlic and 1/2 gallon of water, and bring to a boil. Then, reduce to a simmer.
30 minutes before cooking the turkey, take it out and let it come to room temperature. Coat the bottom of a roasting pan with 2 tbsp of bacon grease.
Cook the turkey for 90 to 120 minutes, making sure not to overcook. The gravy will take 30 minutes, so plan accordingly. When ready, strain into a smaller saucepan and set aside.
After the stock has cooled sufficiently, put it in a blender. Dissolve 1/4 tsp of xanthan gum in 1 tsp of olive oil for each cup of liquid. Add to blender and whiz it up for 10 to 20 seconds. Return to the saucepan.
When the turkey comes out, add the drippings to the gravy and stir until combined. Serve immediately.