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