Add the oil to a large, heavy-bottomed pot and place it over medium heat. Add 2 or 3 popcorn kernels and cover the pot with the lid. Once those kernels pop, the oil is hot enough for the remaining ingredients.
Carefully add the remaining popcorn kernels and sprinkle the sugar evenly over them. Stir quickly with a wooden spoon or give the covered pot a gentle shake to distribute the sugar and oil. Replace the lid, leaving it slightly ajar if the pot design allows safe steam release.
Keep the pot over medium heat and shake it gently every few seconds, holding the lid securely in place. This movement helps prevent the sugar from settling on the bottom and burning. As the kernels begin popping rapidly, continue shaking the pot carefully.
When the popping slows to about 2 seconds between pops, remove the pot from the heat immediately. Do not wait for every kernel to pop, as the sugar can burn quickly near the end. Keep the lid on briefly until the most active popping stops, directing the opening away from your face.
Carefully transfer the hot popcorn to a large bowl or parchment-lined baking sheet. Sprinkle with salt and toss gently using a heat-safe utensil. Spread the popcorn out for a few minutes so the sugar coating can cool and become crisp.
Allow the kettle corn to cool slightly before eating. Break apart any clusters that have stuck together, then serve immediately for the best crunchy texture.