Put the duck fat or oil in a and put it into an oven at 180 degrees.
Peel the potatoes and cut them into 3 or 4 pieces, making sure you keep them all an even size
Chuck the potatoes into a large pan and cover with water, add a bit of salt and cook until they are boiling, lower the heat and simmer for about 2 minutes.
Drain in a colander and then give them a little shake around. Before adding the flour and give another shake to cover evenly.
Add the potatoes to the hot fat. They will sizzle as you do this. You then need to turn each potato until it is covered in the hot fat. Make sure the potatoes are in a single layer before chucking them into the oven for about 35/40 minutes. Make sure you turn each potato every 10 minutes or so, to ensure an even colour.