The Preview app doesn't really have layers like other image editing apps. But you can kinda simulate them with some creative use of copy and paste.
Note: This is Club MacMost exclusive content. To view this video click the thumbnail below to go to the post as Patreon.com. Once there you will be able to view the video as long as you are logged into your Patreon account and a current supporter of MacMost at the "Club MacMost" or higher level.