Peel and slice potatoes, and place them in a saucepan filled with cold water. Season lightly with salt, bring to boil, and cook for 8 minutes. Drain in a colander and allow to steam for 2 minutes. Put back in the empty saucepan, place lid on and shake to scuff up edges.
Add duck fat to large roasting tray, big enough to hold all potatoes in one layer. If you don’t have a tray large enough, split the fat and potatoes over two trays.
Bake in the oven for around fifteen minutes, take out and flip, bake again for 15 minutes, and repeat. Total cooking time should be around 40 minutes, you’re looking for a crispy, golden crust with soft and fluffy center.
Once cooked, serve immediately, adding extra seasoning if need be. Feel free to add whole, unpeeled garlic cloves during baking for delicious roast garlic, or any other veggies for that matter.