Preheat the oven to 200ºC/ Fan 180ºC/Gas 6. Begin by making the sumac paste. Using a pestle and mortar, mix all the ingredients except the garlic, including a little salt and pepper until fully combined.
Add the chopped garlic and pound it into the paste to break it down further.
In a deep roasting tray (ideally one that can be placed on the table to serve), toss the carrots and chickpeas with the cumin and honey.
Drizzle with a little oil. Place the chicken, breast side facing upwards, on top of the veg. Add the pieces of garlic bulb to the tray.
Place the lemon quarters inside the chicken along with the rind of the juiced lemon half you used to make the sumac paste.
Now rub the chicken with the sumac paste, covering the entire surface evenly. At this point, you can cover the chicken with kitchen foil and leave it in the refrigerator for a few hours to marinate, or you can cook it straight away.
Roast the chicken and veg for 1½–2 hours or until the juices from the chicken run clear. Check the chicken after 1 hour, and if it is colouring too quickly, cover it with kitchen foil.
At this point, turn the carrots over as well to ensure they become evenly coloured. You can add a little white wine to the tray if things look dry and you feel some extra juice is required.
Once the chicken and veg are cooked through, cover the bird with kitchen foil, then lay a tea towel on top to help keep it warm. Allow to rest for 10 minutes.
While the chicken is resting, roast the hazelnuts quickly in a small frying pan. Once fragrant and slightly golden, chop them roughly.
Serve the chicken with the hazelnuts sprinkled over the carrots, and allow people to spoon a little of the cooking juices over their meat.