On a clean kitchen towel or paper towels, spread out the frozen hash browns to defrost while you make the dough.

Spray a half-sheet pan (18" x 13") or 9" x 13" pan with nonstick spray, then add 2 tablespoons (25g) of the oil and spread it evenly across the bottom of the pan.

In a large mixing bowl, stir together the mix and yeast.

With a flexible spatula, stir in the hot water and 2 tablespoons (25g) of the oil; mix until combined. The dough will be slack and sticky — that’s OK.

Allow the dough to rest for 10 minutes, uncovered.

Scoop the dough into the prepared pan, flip it over to coat both sides with oil, and gently spread it to the edges of the pan; the dough will be very thin and might not make it to all of the corners if using a half-sheet pan.

Let the dough rise for 30 minutes, uncovered.

At the end of the rise time, gently pat the defrosted potatoes dry with a clean kitchen towel or paper towels.

In a medium mixing bowl, combine the potatoes, rosemary & sea salt packet, and the remaining 2 tablespoons (25g) oil.

Sprinkle the potato mixture evenly across the surface of the dough.

Allow it to continue rising, uncovered, for another 30 minutes.

While the dough rises, preheat the oven to 425°F with racks in the bottom and top thirds.

Bake the potato focaccia on the bottom rack for 30 to 40 minutes, until crisp and well-browned; if the top needs more color, transfer the focaccia to the top rack and carefully broil until golden brown, 1 to 2 minutes.

Let the focaccia cool in the pan for 5 minutes then transfer it to a rack to continue cooling.

Season to taste with salt and black pepper, then serve warm or at room temperature.

Store leftover potato focaccia at room temperature, loosely covered, for up to 1 day, or refrigerate for up to 2 days. Reheat in a 350°F oven until warmed through, about 10 minutes.