stonemason here. 20 yrs exp. i would say scribe wood supports on top of very large stones. the 4 corners should be 1 ton+ size if possible. dig halfway down & water settle the stones for at least 6 months. when they are firmly locked into the earth, begin scribing large posts (12"+) for each individual stone .
i would just do it all with stone. but i love the work involved. if you need stones, check your local quarry or sand company. nothing good ever came easy eh? best of luck!
