Preheat oven to 400°F. Line a baking sheet with parchment paper.
Drain tofu and squeeze block to get more water out of it. Cut into ½ - 1 inch cubes. If you have time, place the cubes on a clean kitchen towel or paper towels and let drain more (placing a heavy plat on top helps).
Transfer the tofu to a shallow mixing bowl. Add tamari and oil and toss to coat. Then add the corn starch and toss again until it is evenly coated.
Pour tofu out onto your baking sheet. Arrange so the cubes are not touching one another.
Bake for 30 minutes, turning halfway through, until golden brown and suitably crispy.