It is about 10" in diameter and completely covered with vintage white buttons. I made it by sewing the buttons to white ribbon (3/8" wide) then wrapping the ribbon around a styrofoam wreath form. I used a few sharp straight pins to secure the button covered ribbon in place (the pins are hidden under the buttons), then tied a ribbon at the top to serve as a hanger.
I keep this wreath up year 'round, hanging from the handle of the door leading to our third floor/attic.
I've seen some smaller versions made as Christmas tree decorations. You could also try glue-gunning the buttons onto the wreath form. Ebay is a good source for buttons in bulk.
How are you decorating for Christmas?