Step 1

Preheat oven to 425°. Spread kosher salt in a 13x9" baking dish. Scrub potatoes, pat dry, and poke a few holes into each; arrange over salt. Roast until flesh is very tender and skins are crisp, 30–40 minutes.

Step 2

Meanwhile, strip leaves from rosemary sprigs and cook with garlic and oil in a small saucepan over medium-low heat, swirling pan occasionally, until garlic is golden, about 3 minutes. Transfer to a large bowl and add potatoes; toss to coat. Serve potatoes generously sprinkled with sea salt.