In a mixing bowl, combine soy sauce, honey, minced garlic, grated ginger, sesame oil, black pepper, and red pepper flakes (if using). Whisk until well mixed.
Place the chicken thighs in a large resealable plastic bag or a shallow dish. Pour the marinade over the chicken, ensuring all pieces are well coated. Seal or cover, and marinate in the refrigerator for at least 30 minutes (up to 2 hours for more flavor).
Preheat the air fryer to 400°F (200°C).
Remove the chicken from the marinade, allowing excess to drip off. Reserve the leftover marinade for basting.
Place the chicken thighs skin-side down in the air fryer basket in a single layer. Air fry for 15 minutes.
After 15 minutes, flip the chicken thighs to skin-side up. Brush the top with some of the reserved marinade. Continue air frying for an additional 10-12 minutes, or until the chicken skin is crispy and reaches an internal temperature of 165°F (75°C).
Once cooked, let the chicken rest for a few minutes, then garnish with chopped green onions before serving.
Notes
Serve with steamed rice and sautéed vegetables for a complete meal.