Cook over medium heat, shaking the pot occasionally. Crack the lid just a smidge so the popcorn stays crisp, and cook until the popping sound slows to about one pop per every few seconds. Remove the pan from heat and dump the popcorn onto the parchment paper-covered pan. Lightly salt it and pick out any kernels that didn't pop.
Once the kernels pop, remove the lid and pour in the remaining popcorn kernels. Cover the pot and give the pot a little shimmy to distribute the kernels evenly.
Cover a large jelly roll pan with parchment paper. Pour the oil into a large, heavy-bottomed pan with a lid (if you have a medium-sized Dutch oven, it's perfect for this). Turn the heat up to medium, add 2 kernels of corn, and cover.