Super easy, although it is a bit time consuming. Save up, beg or find lots of old wine corks. This project again was totally free as I got all the parts straight out of the rubbish bin. :)
Find an old frame. Glue stiff strong cardboard on the back of the frame.
Then start adding the corks with hot glue in what ever design floats your boat. Make sure you set your design out FIRST to make sure they all fit the way you want them to. Once you have your design laid out you can glue away.