Preheat oven to 400 degrees. Spray a large baking sheet with cooking spray or line with a silipat mat and set aside.
Cut each sweet potato in half lengthwise, then again, then cut into evenly sized pieces.
In a large bowl, toss the sweet potato fries with the cornstarch, making sure they are evenly coated.
Pour the oil and seasonings of choice over the fries and toss to coat well.
Spread the sweet potato fries evenly across the pan, making sure to leave a little room between each one.
Bake for about 30 minutes, flipping halfway through.