Well if the lamb was cooked right through to the bone initially as I would hope it was,then,I would just use the cooked lamb straight into a cooking pot with the other ingredients.I personally would put the bone in the pot as well to get the full flavour out of the marrow.I personally would not use a slow cooker for this meal if you are in the house for a couple of hours to give it an occasional stir.I'm afraid I gave my slow cooker away as I don't like cooking with them.I suppose they have their use if you are at work all day and you have a meal waiting for you when you get home,but,you still have to prepare and part cook ingredients beforehand so you might as well let the meal cook on a slow simmer on the hob.It's a matter of opinion/choice at end of day.