Heat 1/3 cup vegetable oil (theaters use coconut oil) until very hot but not smoking (400 to 460 degrees) in a 5- to 6-quart heavy pan with a lid. Add a few kernels-when they pop, add 1 cup kernels in a single layer and put the lid on, leaving it slightly ajar. Shake the pan during popping to keep the kernels from burning. When the popping slows, remove the pan from the heat until the popping stops. Toss the popcorn with fine salt.