In a medium-sized bowl, add flour and 1/2 tsp. salt and 1/8 tsp. pepper. Coat lamb shanks with seasoned flour.
Heat a 12-in. skillet or omelette pan over medium heat until rim is hot to the touch. Add olive oil and heat for an additional minute.
Sear shanks on all sides to a golden brown color. Remove lamb shanks and place in slow cooker.
In the same pan, add onions and cook over medium heat until soft, about 2 minutes.
Add carrots and fennel and continue to cook another 3 - 5 minutes.
Add garlic, bay leaves, thyme bundle and tomato paste. Continue to sauté for about 2 minutes longer.
Add red wine and reduce liquid by half, stirring to scrape bits from the bottom of the pan.
Pour mixture over lamb shanks and add tomatoes with juice, mushrooms and stock.
Cover slow cooker and cook for 8 hours using the Auto setting or cook for 2 hours on High and 6 hours on Low.
At 6 hours, lamb should be falling off the bone; skim fat as necessary from top, remove thyme bundle and bay leaves and adjust seasoning with salt and pepper. Stir in freshly chopped parsley.
Serve with rice, potatoes or crusty bread.