Peel the green plantains by cutting off both ends and making a shallow lengthwise slit along one of the ridges. Use a paring knife to carefully remove the tough skin.
Cut the peeled plantains into 1-inch thick rounds and place in a mixing bowl. Toss with 2 tablespoons of avocado oil to coat evenly.
Preheat the air fryer to 350°F. Arrange the plantain pieces in a single layer in the air fryer basket — do not overcrowd.
Air fry at 350°F for 10 minutes until slightly golden and softened.
Remove from the air fryer. Use a tostonera or the flat bottom of a glass to smash each piece into a flat disk about ¼ inch thick. If they stick, carefully separate with a paring knife.
Return the smashed tostones to the mixing bowl and toss with the remaining 2 tablespoons of avocado oil.
Place back in the air fryer basket in a single layer. Air fry at 350°F for 5-7 minutes, flipping halfway through, until crispy and golden brown.
Sprinkle generously with salt immediately out of the air fryer. Serve hot with garlic mojo or your favorite dipping sauce.