I found some rocks in my back yard that were round(ish) and washed them up really well. Then I used some heavy duty epoxy to glue them together. I usually like to use Devcon High strength 5 minute epoxy but this Loctite worked well too. The Devcon brand was a little less stinky and set up quicker but the end result is the same.
I painted the rocks all white before gluing the hat and carrot on. Paint a face, add some button and scarf and you are done! I decided to glue mine to a board even though he was pretty steady. I have 4 boys who "look with their hands" so I thought it would be better.
I love that snowmen can stay out even past Christmas. They are a winter decoration so they last longer :)