Preheat the oven to 450°F to 500°F
Wash the cast iron with warm water and mild soap if needed
Dry the pan completely
Apply a very thin layer of oil all over the pan, inside and outside
Wipe off all excess oil until the surface looks nearly dry
Place the pan upside down on the middle oven rack
Put a baking sheet or foil on the lower rack to catch drips
Bake for 1 hour
Turn off the oven and let the pan cool inside
Repeat the process 2 to 4 times for a stronger seasoning layer