Step 6: Glue the button

Picture of Glue the button
Using a hot glue gun, squirt a bunch of glue into the center hole, and around the edges of the hole.  Press the shank of the button into the glue filling the center and press down until it cools.

You can also use regular white craft glue, like Sobo, if you don't have a hot glue gun.   You'll just have to wait longer while it dries.