Cut off both ends of the sweet potatoes and peel with a sharp vegetable peeler. Then cut each sweet potato in half lengthwise and again crosswise so you have four pieces.
Slice each piece into 2 or 3 thick slices, then cut each slice into fries. If your sweet potato fries are thinner than that, you'll need to reduce the cooking time.
In a mortar and pestle or spice grinder, grind together coriander, fennel, oregano, and Aleppo pepper (or cayenne). Mix in salt. This makes enough for several batches of sweet potatoes, so you'll need a small jar to store the extra.
Preheat the Air Fryer to 350F/176C while you put the cut fries in a bowl and toss with olive oil, and then with the seasoning mix.
When the preheating is done, add fries to the basket of the Air Fryer, set time for 20 minutes, and push start. Your actual cooking time will probably be less than that. Different Air Fryers cook hotter or cooler, even at the same temperature, so I recommend checking the progress in 3-4 minute intervals as they cook.
Cook the sweet potatoes for 4 minutes without opening the Air Fryer. Then check to see if they’re starting to brown.
We cooked the sweet potato fries 4 minutes more on the first side, adjust that time a bit shorter if yours were already quite brown after the first four minutes.
When sweet potato fries are lightly browned, remove the basket from the air-fryer and use a large turner to quickly turn the fries or shake the basket.
Put the basket back into the Air Fryer and cook 2-4 minutes more on the other side, or longer for some Air Fryer models. Cook them until fries are cooked through and golden brown.
We cooked the sweet potato fries you see in these photos 12 minutes total, turning once. Be sure to check your Sweet Potato Fries at least every 3-4 minutes as they’re cooking.
Serve hot, with Sriracha Aioli Dipping Sauce if desired.