Adjust an oven rack to the middle position and heat the oven to 325 degrees.2. Grease the bottom of a 13 by 9-inch baking dish with 2 tablespoons of the oil and sprinkle half of the garlic across the bottom of the dish. Arrange the tomato slices in the pan, overlapping the edges as needed to fit. Pour the remaining 6 tablespoons oil over the tomatoes and sprinkle with salt and the remaining garlic. Roast the tomatoes until they are slightly shriveled and most of their juices have been replaced with oil, 1 1/2 to 2 hours.3. Remove the dish from the oven and let the tomatoes cool in the oil for at least 15 minutes, or up to 4 hours. To serve, remove the tomatoes from the oil with a slotted spoon (reserving the oil if desired; see note), and season with salt and pepper to taste. (The cooled tomatoes and oil can be refrigerated together in an airtight container for up to 2 weeks; return to room temperature before serving.)
