You will need the following:
A scrap of cardboard big enough to make your wreath on (the size is up to you)
A piece of felt large enough to cover the front and back of your cardboard (either match or contrast with the color of your buttons)
A hefty stack of buttons of all sizes
Hot glue gun (I stole my husband's)
A short piece of rick rack or ribbon for the hanger
A pen and something circular to make your wreath shapes
Hide the spaces by layering the buttons. I did it in a rather haphazard manner, but I think it works for projects like these. The bottom layer is the slightly less interesting buttons, and the upper layers are the cuter ones.