In a large bowl, combine ground chicken, tapioca flour, egg, garlic powder, onion powder, green onions, salt and pepper. Using a wooden spoon or clean hands, stir until well combined. Using a spoon or your hands, roll the meatball mixture into 1 1/4-to-1 1/2-inch meatballs, forming about 24 meatballs. Mixture will be sticky. Add some extra tapioca flour to your hands to help from sticking.