Heat the oil in a large pot with a tight-fitting lid over medium heat. Drop a few popcorn kernels into the oil as a test. Once they pop, add the remaining kernels and immediately take the pot off the heat for about 30 seconds. This allows all the kernels to come to an even temperature, ensuring they pop evenly.

Return the pot to the heat and cover it with the lid, leaving it slightly ajar to vent excess steam and prevent the popcorn from becoming soggy. Shake the pot gently as the kernels begin to pop to prevent burning and to distribute the heat evenly. When the popping slows to just a few seconds between pops, transfer the popcorn to a large mixing bowl.

Drizzle the melted butter evenly over the freshly popped popcorn. Sprinkle with sea salt and nutritional yeast flakes, if using, for a delicious savory flavor. Toss thoroughly to coat the popcorn evenly. Enjoy immediately!