Preheat the oven to 425°F.

Peel, wash, and dry the potato.

Slice off the bottom of the potato so that it sits flat on the cutting board.

Cut ⅛-inch slices across the potato, cutting almost all the way down, but leaving the slices attached. Place chopsticks on either side of the potato to use as guides to keep from slicing too deep.

Soak the sliced potato in a bowl of water to keep it from browning if you are preparing more than one potato.

Slice garlic lengthwise into thin slices.

Insert two slices of garlic into every other slice in the potato.

Insert a sprig of fresh rosemary into the other slices in the potato where there is no garlic.

Brush the bottom of the cast iron skillet with olive oil and sprinkle with salt.

Place the potato in the skillet and drizzle with olive oil. Brush the oil over all sides and down into the slices.

Sprinkle with kosher salt and coarse black pepper.

Place the skillet in the oven and bake at 425°F for 30 minutes.

After 30 minutes, remove skillet from the oven and brush with remaining olive oil.

Return to oven and bake for an additional 30 minutes.

When outside is brown and crispy, remove from the oven and sprinkle with fresh rosemary.