How Deep Should Beans Be?

Hello,

How deep can I make my steamed, innoculated soybeans in the glass dish for fermentation?

I have read that a thin layer three beans deep is as thick as you should go, but on the internet I see people doing it deeper than three beans, and some commercial producers use large, deep boxes.

For home production of natto what is the best thickness of layered beans in the glass fermenting dish?

Thanks,
Tom