Heat the olive oil in a large Dutch oven over medium heat.
Add the ground lamb and cook for 5–7 minutes, breaking it into small pieces until browned.
Stir in the onion, carrot, celery, and garlic. Cook for 5 minutes until softened.
Add the tomato paste and cook for 1 minute, stirring constantly.
Pour in the red wine and simmer for 2–3 minutes until slightly reduced.
Stir in the crushed tomatoes, stock, oregano, thyme, bay leaf, salt, black pepper, and red pepper flakes.
Reduce the heat to low and simmer uncovered for 25–30 minutes, stirring occasionally, until thickened.
Remove the bay leaf and stir in the chopped parsley.
Let the ragu rest for 10 minutes before serving to allow the flavors to deepen.
Spoon over cooked pappardelle or tagliatelle and garnish with freshly grated Parmesan cheese.