Answering the Question: How Places Like Stonehenge Were Built...

 The problem was that we did not have a machine that could reach some of the blocks. The only obvious answer was to break the blocks into smaller pieces with a sledgehammer and load them into a wheelbarrow. To me, this seemed to be too much labor at the time, so I improvised.”

But did they have concrete slabs to work on back then?  Not sure the 2-pebble technique works on soil/dirt, but I suppose they could manage by placing rocks in the path they wanted to travel.  Whatever the case, still impressed.

 "How It All Started"

I am a retired carpenter with  35 years experience in construction. In my work experience, over the years, many times I had to improvise on tools that were not at hand in order to get the job done.

At one of these times, about 20 years ago, I had to remove some 1200 lb. saw cut concrete blocks from an existing floor. The problem was that we did not have a machine that could reach some of the blocks. The only obvious answer was to break the blocks into smaller pieces with a sledgehammer and load them into a wheelbarrow. To me, this seemed to be too much labor at the time, so I improvised.

Using a few rocks and leverage, I removed the blocks from below the floor to an area that the machine could reach them for removal. After doing this several times, the technique became very easy and quick. This experience had me consider the possibility that people may have used this technique before modern day equipment was available.