To season a cast-iron skillet, first preheat the oven to 350°. Wash the skillet in hot, soapy water, and dry it completely. Apply a thin, even coating of shortening on the interior and exterior of the skillet; don’t use vegetable oil as it can leave a sticky film on the iron. On an aluminum foil–lined baking sheet, place the skillet upside down in the oven. Allow the skillet to heat for an hour, turn off the oven, and let the skillet sit until it’s cool to the touch.
You can maintain the seasoned skillet by making sure it’s dried completely after each use. When you first obtain your skillet, it’s a good idea to use it for cooking bacon, frying in oil, or other techniques involving fat, which helps strengthen the seasoning. You will have to occasionally re-season, especially if you use a lot of tomatoes or other acidic foods in the skillet, as they can erode the seasoning.