Preheat oven to 425ºF.

In a small pot, melt butter over medium heat. Add the smashed garlic and the thyme/rosemary along with a heavy pinch of salt and pepper. Turn the heat to low and allow the butter to infuse while you prepare the potatoes.

Gently wash the potatoes (do not peel) under cold water. Dry well.

Once the potatoes are dry, rub about ½ teaspoon of olive oil into the skin of each potato. Place each potato on a cutting board – try to place the flattest side of the potato down. 

Place a wooden chopstick or skewer on both of the long sides of the potato, making sure the chopsticks/skewers are tight against the bottom of the potato and the cutting board. These will help hold the potato in place and ensure you do not cut all of the way through the potato in the next step.

Using a sharp knife, slice each potato crosswise in ⅛-inch intervals, stopping when the knife touches the chopsticks/skewers. 

Gently place the sliced potatoes in a shallow baking dish with the uncut side down, gently fanning each potato out slightly, much like you might do with a deck of playing cards.

Using a basting brush or spoon, generously baste each potato with the garlic butter, making sure to get the butter between the slices of the potatoes. Reserve the rest of the butter for later.

Season each potato with salt and pepper.

Bake for about 1 hour total. Every 15-20 minutes during baking, remove the pan from the oven and brush with more of the garlic butter, making sure it gets between the slices. The potatoes are done when the outsides are golden and the center slices are tender.