Prepare the following, placing each in the same medium bowl as you complete it: Finely chop 10 garlic cloves (about 3 tablespoons); juice 2 medium lemons until you have ¼ cup; add 1 cup ketchup, 1 cup lemon-lime soda, ½ cup packed brown sugar, ½ cup soy sauce, ¼ cup apple cider vinegar, 2 tablespoons oyster sauce, 1 teaspoon ground ginger, 1 teaspoon kosher salt, and ½ teaspoon coarsely ground black pepper. Whisk to combine.

Transfer ⅓ cup of the marinade to a small, airtight container. Pour the remaining into a large zip-top bag. Pat 2 pounds boneless, skinless chicken thighs dry with paper towels. Add the chicken to the bag, seal, and massage to coat the chicken evenly with the marinade. Refrigerate the chicken and remaining marinade for at least 5 hours, or preferably overnight.

Arrange a rack in the middle of the oven and heat the oven to 400ºF. Line a baking sheet with parchment paper and put a wire rack on top of it.

Remove the chicken from the marinade, letting the excess drip off, and arrange in a single layer on the wire rack. Roast for 15 minutes. Flip the chicken and roast until browned, cooked through, and the thickest part not touching bone registers at least 165°F on an instant-read thermometer, 10 to 15 minutes more. Meanwhile, place the reserved marinade in a small saucepan and simmer over medium-low heat until thickened into the consistency of barbecue sauce, about 3 minutes. Remove the saucepan from the heat.

Remove the chicken from the oven and turn on the broiler to high. Brush the reduced marinade onto the chicken, using it all. Broil until browned in spots, 2 to 3 minutes. Garnish with thinly sliced scallions if desired.