Preheat oven to 400°F. Drain the water from the tofu and place on a paper-towel lined plate. Press down for 15-30 minutes with something heavy. I have a panini press that I use but also have heard tofu presses are great as well.
Slice the tofu so you get ½" cubes. In a medium bowl, toss the tofu with olive oil, soy sauce and cornstarch. Toss until everything is evenly coated, being careful to not break the tofu.
Place evenly in a parchment-lined baking sheet and bake for 35-40 minutes, tossing halfway through, until the tofu is golden brown.
Notes
Extra-firm tofu is the only way to go to actually get crispy.
Do not skip placing something heavy over the tofu for at least 30 minutes to release the excess water.
Be consistent with the size you slice the tofu so it cooks evenly.