Use a thickened cardboard base, die-cut the shape of the disc in the middle, and add details for easy removal. Usually, the CD is placed behind the front or back cover, because the cover of the hardcover book is relatively thick, and it is also convenient for craftsmanship to insert the CD. The optical disc was invented by American inventor James Russell in 1965. At that time, the format stored was still mainly analog signals. It is a medium that uses laser scanning to record and read out information.