The way Schmidt sees it, Gobekli Tepe's sloping, rocky ground is a stonecutter's dream. Even without metal chisels or hammers, prehistoric masons wielding flint tools could have chipped away at softer limestone outcrops, shaping them into pillars on the spot before carrying them a few hundred yards to the summit and lifting them upright. Then, Schmidt says, once the stone rings were finished, the ancient builders covered them over with dirt. Eventually, they placed another ring nearby or on top of the old one. Over centuries, these layers created the hilltop.
You can work a soft rock with a hard one. No question. But stone tools cannot be useful as metal ones. Hence, the time required to do the same amount of work is multiplied.
If you want to use a stone tool, you need to create it. With what? What type of stone?
So, lets say they used granite. Is there granite in the area? How did they shape their granite tools? With basalt?