In a cup or small bowl, mix together the unpopped popcorn and oil. Pour the coated corn into a large brown paper bag, sprinkle in the salt and shake to combine. Fold the top of the bag over twice to seal in the ingredients.
Cook in the microwave at full power for 2 1/2 to 3 minutes, or until you hear pauses of about 2 seconds between pops. Carefully open the bag to avoid steam, and pour into a serving bowl.