Having a thriving and sustainable company culture requires ownership at every level--from the leadership team to your front-liners. In your workplace already, there exist employees who are natural culture leaders. Take notice of who they might be. Yes, they can be people on your human resources or people operations teams, but there is probably an unofficial culture leader in every department you have.
You can train these culture teams to facilitate your culture implementation in a localized way. Within these teams, some will be ambassadors, while others will be actual facilitators who can train the rest of your employees on how to bring your ideal culture to life.
To scale culture successfully, you can't just rely on senior leadership or the founders to push it from the top down. Culture is co-owned by leadership and your on-the-ground culture teams to make sure it's bottom-up, too.