Answer:
You first need 5000 tech points to buy construction lvl 2 if you dont already,
then bring a builder to the south west corner and place on the rock pile. (Place more people if you want it to go faster) then when uncovered heat up 4 rocks one at a time... when they get hot justt put a villager on it. Then when all 4 have been laid, there is a plant to the right of the blackberry bush( food) it has big leaves. Place a villager on that after the rocks...
Hope i helped