01 - Preheat oven to 320°F or set slow cooker to low heat.
02 - Generously season lamb shanks with salt and black pepper.
03 - Heat olive oil in a large Dutch oven over medium-high heat. Sear lamb shanks on all sides until richly browned, approximately 8 minutes. Remove and set aside.
04 - In the same pot, add chopped onions, carrots, and celery. Cook for 5 to 7 minutes until softened. Add minced garlic and cook for an additional minute.
05 - Stir in tomato paste and cook for 1 minute. Pour in red wine and scrape bottom of pot to loosen browned bits. Simmer for 2 minutes to reduce slightly.
06 - Add crushed tomatoes, stock, rosemary, thyme, bay leaves, and oregano. Stir to combine evenly.
07 - Nestle lamb shanks back into the sauce. Bring mixture to a gentle simmer.
08 - Cover pot tightly. Transfer to oven and cook for 2.5 to 3 hours or place in slow cooker on low for 7 to 8 hours, until lamb is tender and falling off the bone.
09 - Remove lamb shanks and keep warm under foil. Skim excess fat from sauce and simmer uncovered on stovetop for 10 to 15 minutes to thicken, if preferred.
10 - Plate lamb shanks and spoon sauce over top. Garnish with fresh herbs if desired.