From the UKTelegraph: they used sleds, probably over logs:
“We know that pre-industrialised societies like the Maram Naga in India still use this kind of sledge to construct huge stone monuments. And similar y-shaped sleighs have been found dating back to 2000BC in Japan which we know were used to move megaliths. “The Chinese also used sleighs to build the Forbidden City and some of those blocks are 123 tonnes. So in comparison, these are blocks are quite small.