What you need:
-A washer of desired size
-Wire
-Patterned and/or decorated paper
-Sissors
-Decopauge glue (like Mod Podge)

Step one: Decorate your paper, trace the washer onto it, cut it out.

Step two: 1) Apply a layer of glue, attach paper. Dry for five minutes. 2) Add a layer of glue on top of the paper. Dry fifteen minutes. Repeat 2 as much as desired.
Step three: Repeat one and two for the back of the washer.

Step four: Wrap the wire around the hole in the wire and make a loop at the top.

Step five: Thread string through, and tie off. TADAH!!!

Here are pictures of the front and back of my washer necklace. You can see that I added strips of paper and a stamped flower.