Tear end page from book block, front and back. Cut along opening
Remove paper bound from spine (if applicable).
Can be removed with paste: clamp book block so spine stands up and apply paste (wheat paste) to spine.1) Once covered with paste, cover with gladwrap and allow to sit for 5-10 minutes.
Use blunt knife to scrape off, including mull.2)
Measure and cut new end page. Make sure it is cut to size of book (best to use book as measure as old books may change shape over time