this method works for me........brown the joint on all sides in some melted butter till all sides are sealed. Transfer to the heated slow cooker and place lid on. Brown some chopped onions in the remaining juice in the frying pan, adding a little more butter if needed. Transfer onions to slow cooker. Add half pint of hot beef stock to the frying pan and stir round to collect all the bits and bobs left in the pan and bring to the boil. Add to the slow cooker and cook for recommended time. Take out the meat and keep warm while making the gravy. Transfer liquid to a saucepan and slake a tablespoon of cornflour in a little cold water and add to the stock, which you have brought back to the boil, stirring all the time. Turn down to a simmer and cook for a couple of minutes.
Meat delish and gravy also!