Built one very similar to the one Good Knight referenced. It's lasted almost 8 years. I painted the surface to keep it from soaking in the rain. I also put down gravel to keep the wood from touching ground and allowing the area to stay dry. Two or three of us could move it but it was heavy.
At one pitching facility, they built the base without the plywood and filled it with dirt to create a more natural mound. It required regular maintenance but it was really nice.