At a startup I worked at previously we introduced head-space and heads-down days.

Head space was an experiment where every fortnight, at Friday noon it was tools down and do what ever you want. You were encouraged to go away from the office. Ride your bike, have lunch with your wife/husband or family. What ever you thought was giving you head space.

Heads down days were every Tuesday and Thursday of every week. This meant, on those days no meetings. Work from where ever you want. Turn off Slack. Close your email client. The idea here is "planned" uninterrupted time so you get into the zone for a long stretch of time.

Edit: Oh. Forgot about this. The other Friday afternoon every fortnight we would do "refactor" afternoon. It's were the dev team would come together and refactor parts of the code base as a team. You would get to see parts of the code you'd normally never work on and some really great discussions came out of that.