Soak the grape leaves in a large bowl filled with cold water for about 30 minutes. Remove the leaves and separate them, laying them out on towels to dry. Some of the leaves will be ripped or torn and unsuitable for rolling. Use them to line the bottom of the large, heavy-bottomed pot in which you will cook the stuffed grape leaves.

Bring the water and ½ teaspoon of the salt to a boil over medium-high heat. Add the rice, cover, and turn the heat to low. Cook until the water is absorbed, 17 to 20 minutes. Remove the rice from the heat and let sit, covered, for 2 minutes. Transfer the cooked rice to a large bowl.

In a medium skillet, heat 2 tablespoons of the olive oil. When it is hot, add the onion and garlic and cook until the onion is translucent, about 3 minutes. Add the lamb, ½ teaspoon salt, and pepper and cook until the meat is no longer pink. Add the lamb-onion mixture to the rice along with the pine nuts, dill, parsley, currants, lemon zest, ¼ cup of the lemon juice, coriander, and cayenne. Toss to combine, and season with salt and freshly ground black pepper to taste.

To roll the grape leaves, place 1 grape leaf, smooth side down, on a work surface. Trim the stem if there is one. Spoon 1 tablespoon of the filling onto the leaf near the stem end, and tightly roll the leaf, folding in the sides about halfway and squeezing to pack the filling tightly. (Loosely rolled grape leaves will become soggy and fall apart during cooking.) The size of the rolls may vary according to the size of the leaves. Make more rolls in the same manner. Arrange the rolls in the pot that you have lined with the ripped leaves. Drizzle with the remaining 2 tablespoons olive oil and add the chicken stock and remaining lemon juice to the pot so that the liquid comes up to the top layer of grape leaves. Cover with an inverted heatproof plate and bring the stock to a boil. Cover with a lid and turn the heat to low so that the leaves cook at a bare simmer for about 30 minutes. Remove from the heat and transfer the rolls with tongs to a large platter to cool. Serve at room temperature, or cover with plastic wrap and chill in the refrigerator overnight. Remove from the refrigerator an hour before you plan to serve them.