Cornstarch or arrowroot starch makes tofu extra crispy. Arrowroot is less processed, but it can get a little slimy when added to a dish with a lot of moisture, such as a curry. Cornstarch yields the crispiest results. In addition, adding a little oil to the seasoning gets the tofu even crisper. Make sure not to overcrowd the cubes. Hot air must readily pass between to get them crispy. Toss the tofu halfway to ensure even cooking on all sides. An air fryer yields the best results, but an oven works too.