Preheat the oven to 180°C/350°F/gas 4. Remove any excess fat from inside the cavity of the duck, then using a sharp knife carefully score the breast and legs all over in crisscross fashion, roughly 1cm apart. Season the duck with sea salt, black pepper and the five-spice, then rub all over so the flavour catches in all the nooks and crannies. Halve the clementine and place into the cavity along with the bay leaves. Transfer the duck to a medium roasting tray and roast for around 1 hour 20 minutes. Meanwhile, halve the bulb of garlic across the middle, then peel and roughly slice the carrots and onions. When the time is up, remove the roasting tray from the oven. Carefully lift up the duck and scatter the veg into the tray to make a trivet. Sit the duck on top of the veg, then return the tray to the oven for a further 40 minutes, or until the duck is beautifully crisp and the meat falls easily away from the bone. Once cooked to perfections, remove the duck to a plate to rest while you get on with the gravy. Add the flour to the vegetables, then mash everything together with a potato masher, scraping up all the sticky goodness from the bottom. Place over a medium-high heat, pour in the Marsala and leave to bubble and cook away, stirring well. Add the stock, then bring to the boil and reduce to a simmer for around 15 minutes, or until thickened and reduced. Strain through a coarse sieve, skim away any fat from the surface, then season to taste. Shred or carve up the duck, then serve with the gravy on the side. Nice with duck fat roast potatoes, seasonal greens and cranberry sauce.