Wash the potatoes well and decide whether you want to peel them or leave the skin on for extra texture. Slice each potato into ¼-inch-thick planks, then cut those planks into ¼-inch sticks so every fry is roughly the same size. Keeping the sizing consistent is what stops some fries from turning mushy while others are still undercooked.
Place the potato sticks into a large bowl and cover them completely with cold water. Let them sit for at least 10 minutes, though soaking up to 30 minutes gives even better results if you have the time. This step draws out surface starch, which is the secret to a crispier finish once they hit the air fryer.
Drain the water and spread the fries out on a clean towel or several layers of paper towels. Pat them dry until there's no visible moisture left on the surface, since any leftover water will create steam in the basket. A dry fry is a crispy fry, so don't rush through this part.
Transfer the dried fries into a dry mixing bowl and drizzle the oil over them. Toss everything together until each piece is lightly and evenly coated, then sprinkle on the salt, pepper, and any optional seasonings you're using. Give it one more toss so the seasoning sticks to every fry rather than settling at the bottom of the bowl.
Preheat your air fryer to 380°F for about 3 minutes if your model requires it. Place the fries in a single layer in the basket, leaving a little space between pieces so hot air can move around them freely. If your basket is small, cook the fries in two batches rather than piling them in, since overcrowding leads to soggy, unevenly cooked fries.
Cook the fries at 380°F for about 15 to 18 minutes, pausing to shake the basket or toss the fries with tongs around the halfway mark. Keep an eye on them during the final few minutes, since fry thickness and individual air fryer models can shift the exact timing. Pull them out once they're deeply golden and firm to the touch, then season with a touch more salt while they're still hot.