01 - Preheat 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, honey, olive oil, rice vinegar, black pepper, sea salt, ground coriander, and red chili flakes. Whisk until evenly blended.
03 - Pat the chicken thighs dry with paper towels. Add them to the marinade and toss thoroughly to coat all pieces. Allow to marinate for at least 15 minutes at room temperature, or cover and refrigerate up to 4 hours for deeper flavor penetration.
04 - Scatter the sliced onions and lemon rounds across the bottom of a 9x13-inch baking dish to form an aromatic bed.
05 - Place the marinated chicken thighs skin-side up on top of the onion and lemon layer. Pour any remaining marinade over the chicken evenly.
06 - Bake uncovered for 40 to 45 minutes, until the skin is golden brown and the internal temperature of the thickest part of the thigh reaches 165°F (75°C) and juices run clear.
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. Garnish generously with freshly chopped cilantro or parsley before serving.