1. Soak sweet potato slices in ice water for at least an hour. Dry thoroughly.
2. Preheat oven to 400 degrees F.
3. Toss the potatoes with olive oil then cornstarch. Lay on a baking sheet in a single layer.
4. Grind together spices and sprinkle over potatoes.
5. Bake until crispy on the outside and soft on the inside (25-30 minutes).