Coat the meat with the flour. Saute the onion in the oil and transfer to the slow cooker. Brown the meat and place on top of the onions. Add the mushrooms and herbs, then pour over the soup or stock, and cook on High for 4 5 hours or on Low for 8 10 hours.
NOTE: Any beef casserole can be adapted for the slow cooker, remembering that less liquid is needed than with conventional cooking, and the vegetables must be placed in the bottom of the crockpot with the meat on top.