Maximal tile size for shower stall floor?

I am planning to do a shower stall floor with Silestone tiles. The size is 12"x12".
I am wondering if this size is big for a shower
It seems that with this size it might be difficult to do the slopes?

 

Unless you are doing a linear drain (trench drain along a wall or partition) with a singular angled slope to the floor, 12x12 would not be a great choice for a shower floor. Hand made sloped mud bed shower floors with liner are basically a big bowl (although not as deep). Large tiles will touch on the tips and not touch the floor in the center of the tile. And you certainly will not easily create a bowl out of the large tile. Most tile shower floor are made from 2x2 tiles that will conform to the shape of the mud bed. You are fine to use those 12x12 tiles on the walls.