Using a pair of kitchen scissors, cut along each side of the backbone of the chicken. Discard the backbone. Place the chicken on a flat surface and press down to flatten it. Cut slashes into the skin of the thighs and drums.
Finely chop the basil and coriander. Combine the basil, coriander, lemon juice and zest, olive oil, garlic and salt and pepper. Place the chicken into a large dish. Spread the herb mixture over the chicken. Cover and refrigerate for 30 minutes.
Preheat the oven to 180°C. Place the chicken into a roasting dish and roast for 1 hour, or until the chicken is cooked through. Baste frequently.