1 large sweet potato (about 1 pound)
2 tablespoons potato starch or cornstarch
1/2 teaspoon kosher salt
3 tablespoons vegetable oil
Heat the oven: Arrange a rack in the middle of the oven and heat to 400°F.
Peel and cut the sweet potato: Peel the sweet potato and cut it into 1/4-inch-thick sticks or wedges.
Coat the potato in starch: Place the sweet potato in a large zip-top plastic bag, add the cornstarch and 1/2 teaspoon salt, and shake to combine. (Alternatively, place everything in a large bowl and toss together.)
Coat the potato in oil: Add the 3 tablespoons of oil to the bag or bowl and toss vigorously to coat.
Transfer to a baking sheet: Spread the coated sweet potato wedges out into a single layer on an ungreased baking sheet.
Roast: Roast 15 minutes. Using a flat spatula or turner, flip the sweet potatoes and continue to roast until the fries are tender on the inside and crispy on the outside, 5 to 10 minutes more.
Season and serve: Sprinkle with additional salt if desired before serving.