Spray a 9x13-inch baking dish with avocado oil spray (or any vegetable oil spray). If you want thicker bars, you can use a smaller baking dish.
In a large bowl, mix peanut butter, maple syrup, vanilla, and melted coconut oil together.
Add the rice krispies and stir until evenly coated with the peanut butter mixture.
Transfer the mixture to the baking dish. Spread evenly and press mixture down firmly with a rubber spatula. Refrigerate for at least 30 minutes before cutting into squares and serving.
Notes
Be sure to store vegan rice krispie treats in the fridge when not eating them, so that they'll stay firm.*Please note that these bars do not hold together as well as your classic rice krispie treat, as these don't have marshmallows.