I made these as raffle prizes for the Winter Nerd Battles. They are really easy to do!
Choose some buttons that you feel complement each other and arrange them on some felt of a complimentary color. After you've made a configuration you like, cut the shanks off the buttons that will be on the bottom. Sometimes it works best to leave one or two with the shanks still attached, when they are kind of sitting up on top of other buttons. Definitely leave the shanks attached to the ones on either side of top of the arrangement, and cut a slit in the felt where the shanks on those two buttons will poke through. Glue the buttons on in the arrangement you've chosen (I use E6000) and leave it overnight to set.
After the glue is set, cut the excess felt away from the design.
Use jump rings to attach your chain to the shanks that poke through the felt.
Add your clasp and wear your creation!