Hardback book (This is one I got in Poundland but you can also pick one up in your local charity shop!)
Pen or pencil
White PVA glue
1) In a small dish, mix 50% glue with 50% water, just enough so the glue is runny.
2) Open your book and select the page that you want to be the the first one that will be cut out, for instance, mine has a thicker plain black page so this is the one I'll select. This will be glued down and cut through once the rest of the book is complete.
Apply glue to the 3 edges of the book, apply enough to soak in well but not so much that it's oozing out all over the place!
3) Once the edges are glued, use something like some wooden kebab sticks to separate the first couple of pages from the rest of the book so they don't stick together.
4) Close the book and place a heavy item on top while the glue dries, roughly 15-30 minutes.
5) Once the book is dried, open to the first glued page and draw a 0.5 inch boarder around the edge.
6) Using your craft knife and ruler, cut along the inside lines.
7) After you've cut round the edges, the middle of the page will come away.
8) Keep repeating this process being as neat as you can until you reach the desired depth or the final pages of the book. As you can see, I got a little bit sloppy with mine because I was rushing!
9) Tap out and blow away and small pieces of paper and paper scraps from where you have been cutting. Using some more of your glue solution, coat the inside edges of the book and give the outside edges a second coat. Leave to dry for a couple of minutes and apply glue to the rim of your book and glue down the page you left at the beginning. This will be cut through later.
Close the book, and put a heavy object on the top and leave to dry for another 15-30 minutes.
10) Once dry, cut out the top page of your book as neatly as possible.
11) The inside of your book may still need a little longer to dry so leave it open for another 15 minutes.
12) Once the book is completely dry you can fill it with anything you want to secretly hide away!