01 - Preheat the oven to 400°F (200°C). Position the rack in the center of the oven.
02 - In a large mixing bowl, combine the grated ginger, minced garlic, tamari soy sauce, honey, olive oil, rice vinegar, black pepper, sea salt, ground coriander, and red chili flakes. Whisk until a uniform marinade forms.
03 - Pat the chicken thighs thoroughly dry with paper towels. Add them to the marinade and toss to coat each piece evenly. Allow to marinate for at least 15 minutes at room temperature, or cover and refrigerate for up to 4 hours for deeper flavor penetration.
04 - Arrange the sliced onions and lemon rounds in an even layer across the bottom of a 9x13-inch baking dish.
05 - Place the marinated chicken thighs skin-side up over the onion and lemon bed. Pour any remaining marinade evenly over the top.
06 - Bake uncovered for 40 to 45 minutes, until the chicken skin is deep golden brown and the juices run clear. The internal temperature should reach 165°F (75°C) at the thickest part of the thigh.
07 - For an extra-crisp finish, switch the oven to broil on high for the final 2 to 3 minutes, watching closely to prevent burning.
08 - Remove from the oven and let the chicken rest for 5 minutes. Garnish generously with fresh chopped cilantro or parsley before serving.