Wash the cast iron with warm water and a small amount of mild soap if needed
Dry it completely with a clean towel
Heat it on the stove or in the oven to remove all moisture
Apply a very thin layer of cooking oil to all surfaces, inside and out
Wipe off all excess oil until the surface looks almost dry
Place it upside down in a preheated oven at 450 to 500 F
Put foil or a baking sheet on the lower rack to catch drips
Bake it for 1 hour
Turn off the oven and let the cast iron cool inside
Repeat the oiling and baking process 2 to 3 times for a stronger seasoning
Use the pan regularly and dry it after each wash to maintain the seasoning