Preheat the oven to 150C/300F/Gas 2. Roll out the lamb belly flat on a surface.
Using a sharp knife, score the meat to within 5mm/¼in of the base, in a lattice pattern.
Combine the chopped herbs and spices in a bowl with the oil.
Rub the mixture into all the scored gaps of the meat and place in a roasting tin.
Preheat a grill or griddle to high.
Griddle or grill the lamb for five minutes on a high heat until the outside is crisp and charring.
Roast for one hour 30 minutes, or until cooked through.
If you wish to cook it on a barbecue, heat the barbecue. Fry the lamb in olive oil on a high heat in a frying pan for 10 minutes. Wrap the lamb in foil and poke holes all over.
When the embers of the barbecue are low but constant, leave the foiled lamb to cook for one hour 30 minutes.