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 thoroughly blended.
03 - Pat the chicken thighs dry with paper towels. Add them to the marinade and toss to coat evenly. Allow to marinate at room temperature for at least 15 minutes, or refrigerate up to 4 hours for more pronounced flavor.
04 - Scatter the sliced onions and lemon slices across the bottom of a 9x13-inch baking dish in an even layer.
05 - Place the marinated chicken thighs skin-side up on top of the onion and lemon bed. Pour any remaining marinade over the chicken.
06 - Bake uncovered for 40 to 45 minutes, until the skin is deep golden brown and the internal temperature registers 165°F at the thickest part of the thigh.
07 - For extra-crispy skin, switch the oven to broil on high for the final 2 to 3 minutes, watching carefully to prevent burning.
08 - Remove from the oven and let the chicken rest for 5 minutes. Garnish with fresh chopped cilantro or parsley before serving.