Rub the duck with olive oil, season generously with sea salt and black pepper, and place in a roasting pan.
Place in the oven, and roast for about 2 hours, or until the meat is cooked through.
Remove the duck from the oven, and let rest 10 to 15 minutes.
Remove the duck skin, and shred the meat off the bones.
Melt some cooking fat in a large skillet or sauce pan over medium-high heat.
Add the garlic, celery, and onion, and cook for 5 to 6 minutes, or until soft and fragrant.
Pour the red wine (or some of the chicken stock) into the skillet and cook until completely reduced, scraping up any browned bits from the bottom of the skillet.
Stir in the shredded duck meat, and pour in the chicken stock.
Stir in the blueberries, rosemary and sage. Bring everything to a boil, and let simmer on low for 30 to 45 minutes.
If desired, thicken the sauce by adding-in a mixture of 1 tbsp. of tapioca starch and 1 tbsp. water.
Serve the stew topped with pomegranate seeds and fresh parsley.