Preheat oven to 425˚F (218˚C) and prep half sheet baking tray with parchment paper.
In a large bowl, add tofu cubes, cornstarch, soy sauce and oil. Stir a few times to combine throughly then add tofu to prepped baking sheet.
Using the same bowl, add broccoli, sugar snap peas, oil and salt and pepper to taste. Stir a few times to combine throughly then add to the same baking tray.
Arrange into one layer and bake for 18 - 20 mins or until tofu is golden brown on edges and broccoli is medium hard and bright green.
While tofu and veggies cook, to a small sauce pan add the ingredients for the teriyaki sauce from soy sauce to red pepper flakes. Whisk together over medium heat and bring to a boil.
Add remaining cornstarch and water together and add to the sauce. Whisk together until it thickens, about 1-2 minutes.
When baking is complete, add the tofu and veggies back into the large bowl then cover and toss with preferred amount of teriyaki sauce.