Preheat oven to 425ºF (220ºC). Cut the sweet potatoes into ¼” x ¼” sticks.
Add to a medium mixing bowl, and toss the sweet potatoes with oil until evenly coated.
In a small bowl stir together the cinnamon, sugar and salt. Add the cornstarch and toss to coat followed by the cinnamon sugar mixture, tossing to coat once more.
Spread out the fries in an even layer on a parchment paper lined baking sheet. Bake for 15 minutes then flip the fries over.
Bake for an additional 10 to 15 minutes, until crispy and lightly browned. Serve hot.