This is a great question.
To me, culture is what tells people why they should work, and why they work is what determines how well they work.
Set a context. Make sure that the company is in touch with their why daily.
As you grow, create spaces that can foster increased intimacy.
Keep checking in with the why. Have mentor/mentee relationships. Encourage community, and treat everyone as if they are family.
You're doing so well! Congratulations, and have fun!