Preheat the air fryer to 200 degrees Celsius (392 degrees Fahrenheit).

Cleaning the potatoes: The potatoes should be cooked and eaten with the skin on, so they need to be scrubbed well under cold water. Use a sponge or a brush to thoroughly clean them.

Dry the potatoes well with a clean tea towel or paper towel.

Pour salt and oil into a small bowl.

Make a cross cut on the top of each potato, ideally about halfway through.

Use a small brush to brush the top of the potatoes, the side with the cross cut.

Place the potatoes in the air fryer basket. Make sure they are not too close to each other so that the air can circulate freely around them. Cook them for about 40-50 minutes, depending on the size of your potatoes. Smaller potatoes may require less time (about 30-40 minutes).

Remember to check them along the way to ensure they don't become too brown or dry. Air fryers can vary in efficiency, so adjustments in time may be necessary.

After cooking, let the potatoes rest for a few minutes before serving. They can rest in the air fryer basket, on a rack, cutting board, or plate.

Serve the potatoes warm with a good dollop of butter on top.