How about a shoulder of lamb?

Chop 2-3 carrots, 2-3 sticks of celery and a couple of onions and fry in a little oil until soft - add them to the slow cooker
Place the shoulder on top of them, add a couple of cans of chopped tomato, a generous spoonful of tomato puree, some fresh thyme or rosemary, 5-6 whole, peeled cloves of garlic and finally cover with red wine and/or beef stock.

Bring it up a simmer then cover it up and let it bubble gently away for 5-6 hours until you are ready to serve it...don't worry about overcooking it.

When you want to serve just fish the lump of lamb out and put it on a chopping board - the bone should just pull out of the flesh which makes carving it into portions really easy.
Try to mash to garlic cloves into the sauce a little and spoon it over the lamb - you can serve it with potatoes or rice.

Use any leftovers as a pasta sauce the next day...