Preheat oven to 350 degrees Fahrenheit.
In a medium bowl, combine oats, flour, cornstarch, baking powder, salt, and cinnamon.
In a second bowl, combine sugar and vegan butter with fork, whisk, or beater until well incorporated. Add almond milk and vanilla.
Fold wet ingredients into the dry ingredients until a soft dough develops. Add walnuts and raisins, if desired.
Scoop a dozen 2-3 tablespoon sized mounds of dough on a non-stick lined baking sheet. Flatten each mound just slightly with your fingers or a spoon.
Bake at 350 degrees Fahrenheit for 15-16 minutes, or until a very slightly golden brown rim is forming around the edges of your cookies. Remember, every oven is slightly different, so watch your cookies closely after the 14 minute mark. If you choose to make your cookies smaller (and make more than 12 of them), they won't need to bake as long.
Allow cookies to cool for 5 minutes before lifting off of the baking sheets.
Once cooled, cookies can be stored for up to a week in an airtight container at room temperature.