Preheat the oven to 350 degrees Fahrenheit. Adjust the oven racks so one is in the middle position and the other is at the lowest position.
Wash the grill plate in lukewarm water with mild soap. Rinse with clear water and dry the plate completely.
Rub 1 to 2 tablespoons of vegetable oil over the entire surface of the grill plate, using a clean cloth. Leave behind a thin oil residue on the plate surface.
Set a pan on the bottom rack of the oven to catch any excess oil that drips from the plate as it seasons. Set the plate on the middle rack of the oven, above the pan.
Bake the grill plate for three hours. Add a fresh coating of oil after each hour of baking, if the plate has absorbed the previous application thoroughly.
Turn off the oven and allow the grill plate to cool to room temperature. Lay a paper towel over the cooking surface of the grill plate prior to storage so nothing sticks to the plate, such as dust or other debris.