Here's how I make mine:
Take a 3" square, stamp on it as desired.
Fold it corner to corner.
Open it up and fold it the other way, corner to corner.
Now you should have an "X" on your square with the fold lines.
Using scissors, cut one triangle out.
With the two side triangles, fold one over the center one, put ahesive on it, and fold the other side one over the top of it.
Now you should have a triangle shape with a "pocket" to slip over the corner of your pages!