How thick is the granite usually installed in squares?

Generally, square granite is about 2.5cm, and of course there are thicker ones. It's up to you.

Square bricks are paved with dry mortar, that is, the mixed mortar is dry, and then the mortar is used to plug the joints on the granite.

As for how thick it should be, it is not so easy to determine. It depends on the drainage system of the square. You can generally look at the design drawings of the square.