Put the oatmeal into a basin. Melt the bacon fat in the water and stir into the oatmeal to make a fairly stiff dough. Put on a board dusted with oatmeal and divide into small pieces. Make each into a ball and press down, then roll out very thinly, pressing with the fingers where necessary to avoid cracks. Cook on a hot griddle, hotplate or frying pan. When the oatcakes start to curl at the sides, turn them and bake to a pale biscuit colour.