1.Preheat oven to 230°C (fan-forced). Stuff chicken cavity with bay, 2 lemon halves and 3 garlic cloves, then tie legs together with kitchen string. Finely chop half the oregano and crush remaining 3 garlic cloves. Combine in a bowl with 2 tbs oil, and half the sumac and cumin. Season, and brush over chicken. Line a roasting pan with baking paper and add chicken, breast-side up. Roast for 10 minutes or until slightly golden.
2.Meanwhile, place carrots, onion, chilli, chickpeas, remaining 2 tbs oil, 11/2 tsp sumac and 11/2 tsp cumin in a bowl. Season and toss to combine.
3.Remove chicken from pan. Add the vegetables and remaining lemon to pan, then arrange chicken, breast-side down, on top. Roast for a further 25 minutes or until vegetables are tender, then turn chicken and roast for a final 5 minutes or until golden. Remove from oven, cover dish tightly with foil and rest for 15 minutes.
4.Serve chicken and vegetables with remaining oregano leaves.