Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a mixing bowl, combine ground chicken, breadcrumbs, green onions, grated carrot, minced garlic, egg, salt, pepper, and ginger powder. Mix until just combined.
Shape the mixture into meatballs, about 1 inch in diameter, and place them on the prepared baking sheet.
Bake the meatballs in the preheated oven for 15-20 minutes, or until they reach an internal temperature of 165°F (75°C).
While the meatballs are baking, prepare the teriyaki sauce. In a saucepan over medium heat, mix together soy sauce, brown sugar, pineapple juice, sesame oil, minced garlic, and grated ginger. Bring to a simmer.
Stir in the cornstarch mixture and continue to cook for 2-3 minutes, or until the sauce thickens.
Once the meatballs are cooked, add them to the skillet with the teriyaki sauce and toss to coat evenly.
Cook for 2-3 minutes until heated through.
Serve the meatballs warm, garnished with additional green onions or sesame seeds if desired.