Foxborough State Forest: Propped boulders here and abroad - postage stamps etc

Walking in from Thurston Rd on the south edge of the park, this is a place with many propped boulders and prayer seats. I also saw a few small rock piles.

In Europe, propped boulders are considered man made, and are associated with bronze-age burials. For example Portugal has a series of stamps showing these 'table rocks' or 'dolmen'. But I could not find an example. Instead, here is one from the Bailiwick of Guernsey:and another from Korea
But in America, stalwart armchair geologist are comfortable dismissing these boulders as being a coincidental assemblage dropped by the glacier. It is interesting that no-one has made the statistical argument: that glaciers cannot create many examples of shimmed boulders in one place and none in another. From that point of view, the large concentration of propped boulders in Foxborough is a statistical impossibility. Forthwith, some examples:Oft photo'd:And:
Also saw some prayer seats. This one is formed by a short curve of wall built out from a boulder:
This is a simple 'U'.
Also a few isolated rock piles that were probably associated with the boulders and prayer seats but I am not sure:There were also some examples of very small rocks on top of boulders. Some, in out of the way places, are probably not just trailside whimsy:I wonder if there is a large rock pile site in there somewhere?