Heat 3 Tbsp. oil in a large heavy skillet over medium-high heat. Combine potatoes and garlic in a large bowl; season with salt and pepper. Add potato mixture to hot skillet. Without stirring or moving pan, cook potatoes until light golden brown on one side (this will prevent sticking), 3–4 minutes. Using a spatula, toss potatoes and cook until light golden brown on all sides and cooked through, 8–10 minutes longer.