Preheat the oven to 160°C (fan-assisted).

In a small bowl, mix together the minced garlic, harissa paste, ground cumin, ground coriander, smoked paprika, and ground cinnamon to make a spice paste.

Place the lamb shoulder in a roasting tray and rub it all over with olive oil, then season generously with salt and black pepper.

Spread the spice paste evenly over the lamb, covering it entirely.

Roast the lamb in the preheated oven for approximately 1 hour, or until it reaches your desired level of doneness. For medium-rare, aim for an internal temperature of 55-60°C; for medium, aim for 60-65°C.

Once cooked, remove the lamb from the oven and allow it to rest for 10-15 minutes before slicing.

Garnish with fresh coriander leaves before serving.