01 - Set the oven to 400°F (200°C) to reach desired roasting temperature.
02 - Combine olive oil, sliced garlic, rosemary, thyme, lemon zest, sea salt, and black pepper into a paste in a small bowl.
03 - Dry the lamb with paper towels, make small slits in the meat, then thoroughly rub the herb paste over and inside the slits.
04 - Place the lamb on a rack set inside a large roasting pan.
05 - Toss potatoes in a large bowl with olive oil, sea salt, black pepper, oregano, and lemon juice; arrange around the lamb in the roasting pan.
06 - Pour chicken or lamb stock into the pan around the lamb, avoiding pouring directly over the meat.
07 - Roast for 1 hour 30 minutes, turning the potatoes halfway through. Aim for an internal lamb temperature of 140°F (60°C) for medium-rare.
08 - Remove lamb and potatoes from the oven, cover loosely with foil, and let rest for 15 minutes before carving.
09 - Slice the lamb and serve alongside the roasted potatoes and pan juices.