Place an oven rack in the center and heat your oven to 425°F. Prepare an unlined baking sheet and set it aside.
Set a potato between two chopsticks or skewers to act as a guide.
Slice the potato vertically into thin cuts (about ⅛ inch apart), stopping when your knife reaches the chopsticks so the base stays intact. Repeat with the remaining potatoes.
Transfer the potatoes to the baking sheet. Brush roughly half of the melted butter over each potato, making sure it gets into the slices.
Sprinkle with the measured salt and pepper.
Bake for 30 minutes. After this time, gently separate the slices slightly using a knife, then brush with the remaining butter.
Return to the oven and bake for another 30–35 minutes, until the edges are crisp and the centers are tender. (Timing may vary depending on potato size.)
Serve hot and finish with additional salt and pepper to taste.