Which material should be used for a podium to be tiled?

Thanks again for the tip!

One more question: Is your platform tiled on the side with wall tiles or also on top with floor tiles (so walkable)?

Gladly :)
Our platform is a larger bathroom shelf at the height of the bathtub. It is tiled on top and on the side with wall tiles.
The tiler did everything.

Hopefully you’ll get the stones to the exact height dimension.