Wash potatoes, peel, or do not peel. Soak the cut potatoes in cold water for at least 30 minutes. Drain, and pat dry very well. Place the cut potatoes in a gallon-size sealable bag. Add the amount of oil as desired inside. Seal the bag, and coat all the potatoes with your hands outside the bag. Preheat the air fryer for 3 minutes or the time that your brand says. Place the potatoes in the basket and insert them into the air fryer. Select "air fry" and set temp to (390°F) = (198°C) degrees and set the time to 25 minutes. After cooking for 10 minutes, push pause or stop. Use the tongs to move the potatoes around and return the basket back to the air fryer. Cook for another 15-20 minutes and return the basket until crispiness is desired. Serve immediately after cooking. Sprinkle with salt if desired.