01 - Set the oven to 325°F to prepare for slow cooking.
02 - Pat the lamb dry and season generously with salt and freshly ground black pepper.
03 - Heat olive oil in a large oven-safe pot over medium-high heat. Brown the lamb on all sides, about 3 to 4 minutes per side, then remove and set aside.
04 - In the same pot, add onions, carrots, celery, and garlic. Cook for 5 to 6 minutes until softened and lightly caramelized.
05 - Stir in tomato paste and cook for 1 minute to deepen flavor.
06 - Pour in the red wine, scraping any browned bits from the bottom. Simmer for 2 minutes to reduce slightly.
07 - Return lamb to the pot. Add stock, rosemary, thyme, and bay leaves. Bring to a gentle simmer.
08 - Cover with a tight-fitting lid and place in the preheated oven. Cook for 4 to 4.5 hours, basting occasionally, until the lamb is tender and easily falls apart.
09 - Transfer lamb and vegetables to a serving dish. Skim fat from the cooking liquid and reduce it on the stovetop for a thicker sauce if desired. Serve the lamb and vegetables with the sauce spooned over.