First start with your old book and clean it up as best you can (I'm using "The King's Vixen")
Then draw your outline of the area you wish to cut
Grab the X-acto knife and start cutting!
You should have something resembling this when you're done
Don't throw away the book pages, put them in a baggie to save for other projects
Once all of your pages are out you can use hot glue to glue them all down to each other
If you're going to fill your planter with dirt, line the inside of the book first with something like plastic wrap or a piece of a garbage bag
Add some decorative rocks and flowers and you're done 😊