Preheat the oven to 425°F (220°C). Line a baking sheet with parchment paper.
In a mixing bowl, combine the olive oil, tamari, and sriracha.
Add the cubed, patted-dry tofu to the bowl and gently toss until evenly coated with the sauce.
If using cornstarch, sprinkle it over the sauced tofu and toss gently to coat each piece for extra crispness.
Spread the tofu in a single layer on the prepared baking sheet so pieces are not touching.
Bake for 20 to 25 minutes, turning once if desired, until the edges are browned and the tofu is crisp.
Remove from the oven and serve warm.