There are so many little things you can do to make everyone feel welcome and comfortable, a lot of companies do these things for women and minorities but everyone benefits.

-regular checkins -coaches/mentors -make sure that everyone participates in meetings/dev huddles. Often toxic environments stem from just a few individuals who are louder than everyone else. No one else is ever heard and doesn't feel like part of the team. -make sure people feel empowered to do their job and more. get rid of micromanagers. -management should be open to feedback and act on it.

Feedback is the key ingredient. Make sure employees have a channel to voice their opinions and that it is acted on.