01 - Preheat the oven to 400°F. Position the rack in the center.
02 - In a large mixing bowl, combine the grated ginger, minced garlic, tamari, honey, olive oil, rice vinegar, black pepper, salt, ground coriander, and chili flakes. Whisk until smooth and well blended.
03 - Pat the chicken thighs dry with paper towels. Add them to the marinade and toss thoroughly to coat each piece evenly. Allow to marinate at room temperature for at least 15 minutes, or refrigerate for up to 4 hours for deeper flavor penetration.
04 - Arrange the sliced onion and lemon 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 slices. Pour any remaining marinade evenly over the top.
06 - Bake uncovered for 40 to 45 minutes, until the skin is deep golden brown and the juices run clear. The internal temperature of the thickest part of the thigh should register 165°F.
07 - For an extra-crispy finish, switch the oven to broil on high for the final 2 to 3 minutes, watching closely to prevent burning.
08 - Remove the dish from the oven and let the chicken rest for 5 minutes. Sprinkle with fresh chopped cilantro or parsley before serving.