Heat cast iron skillet (or any heavy-bottomed pan) over high heat until very hot. Add oil to hot skillet. Place scallops in skillet, seasoned side down, ensuring they have enough space to sear without steaming each other. Prepare in batches, if necessary. Sear for about 2 minutes until a golden crust forms. Turn over and cook for about 1 minute more. Remove from heat immediately to avoid overcooking and transfer cooked scallops to clean plate.