Preheat your air fryer. Set it to 400°F (200°C) and let it warm up for 5 minutes.
Scrub potatoes well under running water. I don't peel them as leaving the skins on adds crispiness and fiber. Just remove any dirt on the outside.
2 cups russet or Yukon gold potatoes
Dice the potatoes into ½-inch cubes. To do this place each potato on a cutting board. Cut lengthwise into ½-inch thick slabs. Stack 2-3 slabs, then slice them lengthwise again into ½-inch wide sticks (like thick French fries). Rotate the sticks 90 degrees and cut across into ½-inch cubes. If using smaller potatoes, cut in half and then half again. Try to keep all cubes roughly the same size. Even cubes = even cooking and crisping.
Pat them dry with a clean towel to remove excess moisture.
Toss potatoes with olive oil, rosemary, and salt until evenly coated.
½ tablespoons olive oil, 1 teaspoon dried rosemary, ¼ teaspoon salt
Spread the potato cubes in a single layer in the air fryer basket.
Cook for 16-18 minutes at 400F, shaking at 8-9 minutes and shaking them well.