Step 1

Bring a small saucepan of water to a boil. Place apricots in a medium bowl and pour in boiling water just to cover; reserve saucepan. Let apricots soak 10 minutes, then drain. Set aside.

Step 2

Meanwhile, mix salt and ras-el-hanout in a small bowl to combine. Mix garlic, harissa, and preserved lemon paste in a medium bowl to combine. Mix oil, 1½ tsp. salt mixture, and ¼ cup harissa mixture in another small bowl; set oil mixture aside for roasting vegetables.

Step 3

Rub 2 Tbsp. harissa mixture all over lamb, then coat lamb with remaining salt mixture, pressing to adhere. Coat lamb with remaining harissa mixture. Place in a large roasting pan and cover with a sheet of parchment paper, pressing firmly to adhere to meat and tucking in ends. Let lamb sit on the counter at room temperature at least 2 hours, or chill overnight. If chilling, let meat sit at room temperature 2 hours before roasting.

Step 4

When you’re ready to roast lamb, place a rack in middle of oven; preheat to 300°. Toss potatoes, onions, and fennel in a large bowl with reserved oil mixture to coat, then toss in reserved apricots just to distribute.

Step 5

Bring 1½ cups water to a boil in reserved saucepan. Remove parchment paper from lamb and arrange vegetables around; pour boiling water into roasting pan. Place a fresh sheet of parchment loosely over lamb and cover with a sheet of heavy-duty foil, crimping tightly around edges to seal. Slide pan into oven and place a large rimmed baking sheet on rack below roasting pan to catch any drips. Bake until lamb is fork-tender, 5½–6 hours. Remove pan from oven and let lamb rest 30 minutes before uncovering.

Step 6

While the meat is resting, halve fennel bulb and thinly slice on a mandoline or with a knife. Toss fennel and herbs in a medium bowl to combine, then add oil and preserved lemon paste and toss to coat.

Step 7

To serve, place lamb on a large platter and arrange vegetables around. Pour some of the roasting juices over. Top with some of the fennel salad; serve remaining salad and a bowl of any remaining roasting juices alongside. As you pull the meat from the bone, you can moisten it with juices if desired.