The first step is cleaning the ball. I used isopropyl alcohol to remove years of bowling alley oil and palm sweat from the ball.
You want to leave one hole open for mounting the ball in your garden. I left the thumb hole open because it's larger than the others and gives more options for mounting.
Using a clear, exterior grade caulk, glue the glass stones to the ball. It just takes a dollop of caulk. Press the stone to the ball firmly. The weight of the glass will cause it to slide down the curved surface if you don't hold it in place for many minutes. I found that a large rubber band placed around the middle of the ball not only marked a straight line, but also helped hold the stones, reduced their slide, and didn't require me to waste time applying continual pressure.
You'll need to let the first layer set up and dry before moving on. The weight of more than one row will be too much for the rubber band and many pieces will drop off, but with the first row intact it provides an anchor for successive layers. After a few hours of allowing the caulk to set it should be strong enough.
When the entire ball has had a few days to dry completely it's ready to place outside. Rebar is an easy mounting rod. Galvanized pipes can be used and can be painted to match the ball. Copper pipe adds a nice touch and brings an eclectic look when is develops a patina.
Their is no limit to the colors and designs that you can use to make gazing balls. After the gold ball with colored glass I made a silver one with clear glass stones.
With a little imagination, a bowling ball, and minimal crafting skill, you can have a gazing ball of your own.