Remove the chicken from its packaging, discard any giblets, pat it dry inside and out with kitchen paper, and, if you wish, truss it by tying the legs together with kitchen string and tucking the wing tips underneath.
In a small bowl, whisk together the olive oil, coarse sea salt, black pepper, garlic powder, onion powder, smoked paprika (or paprika) and dried thyme (or rosemary).
Place a roasting rack inside a roasting tin and set the chicken breast-side up on the rack. Rub the seasoned oil all over the chicken, making sure to get under the wings and into any crevices.
Stuff the cavity with half a lemon, half a medium onion and the smashed garlic cloves.
Preheat the oven to 220°C (200°C fan)/gas mark 7.
Roast at 220°C (200°C fan)/gas mark 7 for 20–25 minutes, until the skin is golden-brown and crisp.
Reduce the temperature to 190°C (170°C fan)/gas mark 5 and roast for another 50–70 minutes, until a probe thermometer inserted into the thickest part of the thigh reads 74°C and the juices run clear.
Transfer the chicken to a carving board, loosely cover with foil and leave to rest for 10–15 minutes.
Carve the chicken and serve with your choice of side dishes.