Pour the turkey drippings into a saucepan, and gradually whisk in the flour. Bring the mixture to a simmer over low heat and cook until the mixture is a golden brown color, stirring occasionally, about 5 minutes. Gradually whisk in the turkey stock until the gravy is smooth; mix in a little water if desired. Season to taste with salt, black pepper, and celery salt, then simmer about 15 more minutes to thicken the gravy and blend the flavors.
