In a large ovenproof dish, start layering with a layer of potatoes, layer of onions, layer of corned beef. Top with another layer of potatoes, layer of onions and then layer of 1/2 the smoked bacon. Finish with a layer of potatoes and pour over your stock and season with salt and pepper.
Cover with foil, place in a pre-heated 180 C / Gas 4 oven for 1 1/2 hours. Remove and add remaining bacon on top and place back into the oven for a further 30 minutes.