01 - Preheat oven to 400°F. 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, salt, coriander, and 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. Let rest for at least 15 minutes at room temperature, or cover and refrigerate up to 4 hours for deeper flavor penetration.
04 - Scatter sliced onions and lemon across the bottom of a 9x13-inch baking dish. Arrange the marinated chicken thighs skin-side up over the onion and lemon layer. Pour any remaining marinade over the top.
05 - Bake uncovered for 40 to 45 minutes until the skin is golden brown and the internal temperature registers 165°F at the thickest part of the thigh.
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 from the oven and let the chicken rest for 5 minutes. Garnish with freshly chopped cilantro or parsley before serving.