there are some tips here on the Open Spaces post at Spotify Labs: https://labs.spotify.com/2017/05/31/going-into-deep-space-creating-the-right-environment-for-your-open-space/
Generally provide for structured space for sessions, and for casual spaces for people to continue outside of the program if they wish.
My last unconference was in a factory hall which was great. It provided 2 closed rooms for sessions, and then an opportunity in the factory hall to for 3-5 bean-bag type circles, or just picnic tables to sit and drink coffee if they wanted to. It was really a chilled atmosphere. People from the factory (a maker space, actually), would still be working around, and the one thing didn’t interrupt the other.
Having the board in the open space was also really great, as it helped enforce the law of 2 feet more easily.