Wash the potatoes. Place them in a medium large pot and cover with water. Heat over high heat to bring to a boil.
Reduce heat to medium high. Boil the potatoes for 30 – 40 minutes until they are soft.
Drain the water from the potatoes.
Gently and lightly smash each potato to break open the skin and/or break into 2 – 4 pieces.
Place the smashed potatoes in a large skillet. Heat on medium. Add 2 Tbsp oil. Sprinkle the salt and rosemary over the potatoes. Stir gently.
Cook for 7 minutes. Gently turn the potatoes over. Stir/flip every ~7 minutes, adding more oil as needed. It is important to let the potatoes sit long enough between stirrings so that they will get crispy.