Wash the skillet with hot water and a small amount of soap if needed
Dry it completely
Heat the skillet on the stove or in the oven to remove any remaining moisture
Apply a thin, even layer of cooking oil to the entire surface, inside and out
Wipe off all excess oil until it looks nearly dry
Place the skillet upside down in a preheated oven at 450°F to 500°F
Put foil or a baking sheet on the lower rack to catch drips
Bake for 1 hour
Turn off the oven and let the skillet cool inside
Repeat the oiling and baking process 2 to 3 times for a stronger seasoning
Use the skillet regularly and avoid soaking it in water