Heat about half the olive oil in a large stockpot over medium-high heat. Add the turkey wings and brown. Remove the turkey wings and add the remaining oil, onion, carrots, garlic, herbs, and peppercorns and cook for 5 minutes, scraping the brown bits on the bottom of the pan. Return the wings to the pot and add chicken broth. Bring to the boil, skimming any foam that rises to the surface. Reduce the heat and simmer for about 1 1/2 to 2 hours. Strain out and discard the solids and set aside the stock.
Once your turkey has roasted, set the pan over medium heat on the stove top. Discard some of the fat if there is too much (you'll need about 1/4 cup). Add the butter and cook until melted. Add the flour to the pan and, using a whisk, stir constantly to incorporate the fat and flour. Once you have a consistent paste add the warm stock in a steady stream while you stir to work out any lumps. Cook until the gravy has thickened, about 10 to 15 minutes. Season well with salt and pepper and serve.