01 - In a large mixing bowl, whisk together the buttermilk, olive oil, minced garlic, kosher salt, black pepper, paprika, dried thyme, lemon zest, and lemon juice until thoroughly combined.
02 - Place the spatchcocked or sectioned chicken into a large zip-top bag or non-reactive container. Pour the marinade over the chicken, ensuring every surface is evenly coated. Seal tightly and refrigerate for a minimum of 8 hours, preferably overnight, for optimal flavor penetration.
03 - Remove the chicken from the refrigerator and take it out of the marinade, allowing any excess to drip off. Discard the used marinade. Pat the chicken lightly with paper towels to remove surface moisture, then brush evenly with olive oil to promote browning.
04 - Preheat the oven to 425°F. Set a wire rack over a rimmed baking sheet and arrange the chicken on the rack, skin-side up, to allow even air circulation during roasting.
05 - Roast the chicken for 45 to 60 minutes, or until the skin turns a deep golden brown and the juices run clear. Verify doneness by inserting a meat thermometer into the thickest part of the thigh—it should register 165°F.
06 - Transfer the chicken to a cutting board and let it rest for 10 minutes to allow the juices to redistribute. Carve into serving pieces, garnish with fresh herbs if desired, and serve warm.