Flour or cornstarch? Premix with milk or water? Avoid lumps?
I favor no thickener. After removing the turkey from the pan, place the roasting pan over medium heat. Add enough wine (red or white) to just cover the base of the pan. Bring to a boil and use a wooden spoon to scrape up the pan drippings. Add 4 cups broth (chicken or turkey) to the pan, bring to a boil. Add some herbs -- a few sprigs thyme, a garlic clove, a bay leaf -- to the broth, and let it boil down until it's syrupy. It will never get "thick" but it will intensify in flavor and become viscous. When you don't add cornstarch or flour, you get a very clear and intense gravy. Season with salt at the end. Happy Thanksgiving!