Preheat oven to 400 degrees. Coat a baking sheet with non-stick cooking spray. To assemble the galette, overlap potato slices in a ring about 4 inches in diameter. Arrange a second, slightly smaller ring on top of the first. Form a second galette in the same manner. Brush the gallettes with oil and season with salt and pepper. Bake for 25 to 30 minutes, or until the potatoes are tender and golden. Using a wide metal spatula, carefully transfer the galettes to individual plates and serve.