Place the flour and cornstarch in a bowl. Add salt and mix. Then add in the cold, cubed vegan butter.
Use a fork or a pastry cutter to "cut" the butter into the flour. This is fancy speak for breaking the butter into smaller, pea-sized particles so it mixes evenly and gives the flour a grainy texture. See pro tips above for more details.
Drizzle ice cold water, a tablespoon at a time, into the flour-butter mixture while mixing with a fork. Stop as soon as the dough begins to come together and you don't have any dry flour remaining in the bowl.
Divide the dough into two. Wrap each half tightly in cling wrap, shaping the dough into a disc with your hands as you do so. Refrigerate the dough for at least 15 minutes before rolling it out. This will give the butter time to harden up again before you bake it.
Roll out the crust. Flour a cool surface, like a marble or granite countertop or a large baking sheet that has been refrigerated for at least 15 minutes. Place one disc of the pie dough on the surface and, using a floured rolling pin, roll it into a circle two inches larger than the diameter of the pie plate.
Transfer the crust to the pie plate. Fold the crust in half and, if you wish, fold it once more. Lift the folded crust carefully and place it in the pie plate. Unfold gently and fit it into the pie plate.
Tuck any overhanging dough under the edges. Don't trim away any excess dough! This is tasty stuff and you want all of that flaky crust you can get, so just tuck the excess in until you have an even edge. Then use your fingers to flute the edges in a decorative pattern, or press the tines of a fork into the edges.
Refrigerate the pie crust for 15 minutes before baking. This will help the butter harden up again and ensure a flakier crust.
Bake the pie according to directions. This will vary slightly for different pie fillings but should roughly be around 50 minutes to an hour. For my strawberry pie, for instance, which is a double crust pie, I bake the pie at 425 degrees for 20 minutes, and then at 400 degrees for 30 more minutes.