Step 1Bring 4 cups of water, the salt, peppercorns, cloves, coriander seed and cinnamon to a rolling boil, then set it aside to steep for 10 minutes. Add the cider and cool to room temperature.
Step 2Place the pork roast in a large plastic bag and pour the cider mixture over the top. Seal tightly and refrigerate at least 2 days.
Step 3Heat the oven to 300 degrees. Place the roast upside-down in a roasting pan so that it is supported by the rib bones. Roast 30 minutes, then turn the meat over and continue cooking to an internal temperature of about 140 degrees, 2 to 2 1/2 hours longer.
Step 4While the roast is cooking, peel the vegetables and cut them into about half-inch pieces. The shapes need not be consistent, but the sizes should be. You will have 5 to 6 cups of cut-up vegetables.
Step 5Melt the butter in a large skillet over medium-high heat and stir in the salt, sugar, wine, vinegar, cloves and orange zest. Stir in the vegetables, cover and cook until the vegetables begin to become tender, about 10 minutes. There should be a lot of liquid in the pan.
Step 6Remove the lid and increase the heat to high to evaporate the liquid. Cook until the vegetables are covered with a shiny glaze and begin to brown, about 5 minutes. Stir carefully to avoid breaking up the vegetables. Add the nutmeg, parsley and hazelnuts and adjust the seasoning for salt and vinegar.
Step 7When the roast is ready, spoon as much of the vegetable mixture as possible into the center of the crown roast, spoon some of the fat from the bottom of the roasting pan over the stuffing, and return the meat to the oven. Cook the roast to an internal temperature of 145 degrees, an additional 10 to 15 minutes.
Step 8Transfer the roast from the pan to a platter and let it rest for 10 minutes before serving. Discard all but 1 to 2 tablespoons of the rendered pork fat from the roasting pan. Place the pan on the stove over medium heat and gently stir the remaining stuffing in the pork drippings. Transfer this to a bowl and keep warm before serving alongside the roast.