Fondant Potatoes

Name: Fondant Potatoes
Ingredients: 5 large Yukon Gold potatoes, about 3 pounds; 1/2 teaspoon fine salt; 1/2 teaspoon freshly ground black pepper; 1 tablespoon vegetable oil, lard, or schmaltz , more as needed; 4 tablespoons (¼ cup) unsalted butter, cubed; 2 large cloves garlic, peeled and smashed; 2 sprigs fresh thyme, more for garnish, optional; 2 sprigs fresh rosemary, more for garnish, optional; 1 1/2 cups chicken stock; Zest and juice of 1 medium lemon; Flaky salt, for garnish