Place oven rack in upper-middle position. Heat oven to 500 degrees. Set wire rack in a rimmed baking sheet.
Bring 2 quarts of water to a boil in a Dutch oven or large pot. Add potatoes and salt and cook until potatoes are just tender, about 20 to 30 minutes. Drain potatoes and place them on the wire rack to air dry for 10 minutes.
Coat a baking sheet with the 6 tablespoons of olive oil.
Place potatoes on greased baking sheet, spacing them evenly. Use the underside of a measuring cup to flatten each potato to 1/2-inch thickness.
Brush potatoes with 1 1/2 tablespoons of the malt vinegar and season with pepper.
Roast until potatoes are browned, about 25 to 30 minutes.
Brush with remaining vinegar and serve.