Heat pan drippings on med/high. Sprinkle in the flour and cook, stirring constantly for 2-3 minutes.
Pour in the stock, and cook (whisking constantly) on med/high to high for another 5 minutes or until thickened to desired consistency. If it gets too thick, you can add a small amount of water or more stock, a little at a time. Gravy thickens a little as it cools, so a bit thinner now will be a bit thicker by the time you serve.
*See note below for general gravy rules.
A good rule of thumb for gravy is however many tablespoons of fat (butter, bacon grease, oil, pan drippings, etc.) you’ll use equal amounts of flour and that number in cups of liquid. IE: 2 tablespoons fat, 2 tablespoons flour, 2 cups liquid.