Rinse and peel the potatoes. Remove the "eyes". Rinse under cold water, and cut into 2" wide chuncks.
Transfer all the potatoes chunks to the sauce pan, and add cold water to cover potatoes.
Place the pan on the stove, turn heat to high, bring the water to boil, turn heat to low, and simmer for about 15-20 minutes or until the potatoes start breaking up on the edges and the center is soft. You can stab the potatoes with a knife, and if the chuck can't be stuck on the knife, it's done. Drain the potatoes.
Place the frying pan onto the stove, add the duck fat, and turn heat to high.
Spread the cooked potatoes chunks in the frying pan. Once the fat/potatoes start sizzling, turn heat to low to medium.
Roast all sides of the potatoes at low to medium heat. It takes about 20 minutes.
Once all sides of the potatoes are golden/brown, add the dried thyme and rosemary. Roast for another 3-4 minutes. Sprinkle the salt, and roast for 1-2 minutes.
Plate and serve while hot