Foster creativity and community building. Creativity helps people think outside of the box. It helps them benefit from aggregate brain usage and synergistic intelligence. Any creative activity will do, from art or music to dance, but my favorite is improvisational theater. If I'm mirroring everything someone does, we're going to start laughing.
Levity builds community and makes people more creativity.
Offer an outside facilitator. Have an outside, trained facilitator regularly meet with your employees to discuss their concerns. Inside people are just not trusted the same way as an outsider. The facilitator should listen to what the employees say and communicate it to management, which will address the concerns. You don't have to do everything your employees ask for, but you have to show them that you are paying attention to what they have to say.