Bring potatoes, with water to cover, to boil over medium-high heat in a large, covered pot. Reduce heat to medium-low and continue to boil until potatoes are just tender, about 30 minutes. While potatoes boil, adjust oven rack to lowest position and heat oven to 450 degrees. Drain the potatoes and turn onto a large, oiled baking sheet. Use a potato masher to crush each potato. Drizzle with oil and sprinkle with salt and pepper. (Can be covered and refrigerated overnight; bring to room temperature.) Bake until crisp and golden, about 20 minutes. Remove from oven and spread a portion of garlic and sprinkle a little thyme over each potato. Return to the oven and continue to roast until golden brown, about 10 minutes longer. Serve immediately.