Coat the tofu in starch: Add about half the cornstarch (or another starch of choice to the bottom of a mixing bowl. Add in the tofu and pour the remaining starch on top. Then use your hands or a flexible rubber spatula to gently toss the tofu until it's thoroughly coated with the starch. Let the tofu sit in the starch while you heat the oil.
Prep your frying pot: Add your frying oil to a pot or pan. Personally I like to use a heavy pot (a Dutch oven or cast iron skillet), because it will retain heat and keep the temperature stable while frying. I also like to use a pot with high sides to avoid splattering, but this is optional. I usually need to use about 2-3 cups of oil in my pot, but you might need more if yours is larger.
Heat the frying oil: Heat the oil over medium-high heat until it reaches 400°F. I like to fry these at around 350-375°F, but the temperature will drop once the tofu is added, which is why I start at 400°F. A thermometer is highly recommended to monitor the temperature.
Prep your space: While the oil heats, set up a spot for your tofu once it's fried. I like to use a wire cooling rack over a cookie sheet. You can use a paper towel lined plate if you prefer.
Add tofu to oil: Once the frying oil reaches 400°F, carefully add your starch-coated tofu pieces. Give them a quick stir just to ensure they aren't sticking to the bottom of the pot, then let them fry undisturbed for about 1-2 minutes. At this point some of the pieces may be sticking together slightly. Carefully peel them apart. (I usually use two forks to do this, but be cautious of the oil splattering.) Some starches stick more than others — see notes.
Fry until crispy: Fry the tofu pieces for 5-6 minutes in total, stirring occasionally, until they are very crispy. Starch won't develop a deep golden brown color in the same way that flour would, but they will be slightly golden brown when they are ready.
Remove tofu: Turn off the heat. Use a metal spider, slotted spoon, or tongs to remove the crispy fried tofu to the rack or plate you prepared earlier.