For the crispiest oven-baked sweet potato fries, you need to walk over to the pantry and take out the cornstarch because that ingredient is the secret.
Peel and cut sweet potato into 1/4-inch-thick sticks or wedges.
Place sweet potato in a large zip-top plastic bag, add the potato starch or cornstarch and salt, and shake to combine.
Add oil and toss vigorously to coat.
Transfer to baking sheets and spread into a single, even layer, leaving space around each fry.
Roast at 400°F until some of the edges are just starting to brown, about 15 minutes. Flip the fries and then bake for another 5-15 minutes.
Season and serve. Sprinkle with more salt if desired before serving.