Preheat the air fryer to 425 degrees F. In a small bowl, whisk together water, garlic, and 1 teaspoon of salt. Set aside.
Chop off the ends of the plantain. Then, slice the plantain lengthwise, only slicing skin deep. Pull away the peel with your fingers.
Cut the plantain into 1-inch chunks. Toss or brush plantains with oil.
Arrange plantain chunks into the air fryer basket. Air fry for 6 minutes.
Remove the plantains from the air fryer and smash them flat with the back of a small plate or mug. Dip each tostone into the water for about 5 seconds. Tap off excess water.
Toss or brush plantains with oil.
Return the plantains to the air fryer and air fry for 5 minutes. Remove from the air fryer and immediately season with salt.
Notes
Be sure to use unripe plantains. Unripe plantains are firm and green.