If that is the case, there is no rule for transcribing a book jacket. In my experience, the book jacket is not included in the transcription. If you are required to include it, it belongs in the p-pages with material from the back cover, inside front cover, etc. with no print page number. A tn would explain its location in print.
I don’t believe there are any rules covering your overlay process. You would follow Formats rules for the text. Here are a couple of suggestions for creating overlays. Stagger the location on the pages so that all of the plastic is not at the same level on every page. Round off the corners of each plastic application. Rounded corners make it more difficult to peel the plastic off the page. Very important — proofread carefully before actually sticking it on the page.