Heat the oven to 250 C
Cut the sweet potatoes into sticks 1/4 to 1/2 inch wide and 3 inches long, and toss them with the oil.
Mix the spices, salt and pepper in a small bowl, and toss them with the sweet potatoes. Spread them out on 2 rimmed baking sheets with parchment paper.
Bake until brown and crisp on the bottom, about 15 minutes, then flip and cook until the other side is crisp, about 10 minutes. Serve hot.