Thank you. Do I need to use some kind of metal mounding bracket inside the wall or can it rest on a wood frame?

ideally use one because when people will sit on it , the impact may move it so will be good to have it anchored with the bracket as a extra precaution . all the luck , Planning a Diy ?

This slab would NOT go into the wall, it would only get fabricated after the shower gets created. (looks like the tile on the wall above was done after the bench was installed)
It more than likely has sufficient support under it, not seen in this picture, but rest assured, it would not need to go INTO the wall!

Hopefully the original designer will post a reply to clarify what kind of support he used, but until then, show the photo to your stone supplier and your contractor,they will tell you what needs to be done to support the stone.

Thank you all for your comments. I'll check with the stone supplier. I am not doing this work myself. My contractor has not worked with a floating type granite bench before and I want to be sure that this is done correctly to prevent injury and costly mistakes . I read somewhere that a bench this heavy needs steel support and that the 2x4s are notched in so that the edges of the bench are not resting on the tile edges but rather in a U channel attached to the 2x4s.

Absolutely the slab is NOT resting on the tile edges, that would be incredibly dangerous.
But whatever support was used, there is most definitely additional support, hidden from view.

I believe this granite is not as thick as it looks, I would bet that the edges are mitered to make it look thicker.

The support is a steel u channel and it IS as thick as it looks. I have been enjoying it for 2 years now.

Awesome, it's beautiful!

Twink likes it , too!