At London Academy of Excellence, we have;
1) A very proactive flexible working policy for teachers and non-teachers, right from the point of advertising (where we'd almost always advertise roles as full or part time), to interview, to regular reminders about the possibility of flexible working requests. This means that nearly 50% of our staff work part time, which has a significant impact on wellbeing in our experience.
2) A line management policy which makes wellbeing (of both staff and students) the first item in all meetings, with flexible application of leave of absence policies the norm.
3) An engaged staff consultative group who meet regularly with me to ensure that staff voice genuinely feeds into the development planning cycle for the school.
4) A (small but important) culture of staff thank yous in every Friday briefing (staff nominate each other) and one nominee is chosen each week for a small prize, with other nominees all receiving a thank you email every Friday. We've done this for more than two years and it is really good for staff morale!
To be honest, more important than any of this is a culture and values which nearly all staff understand and buy into. We try very hard to frame everything we do in terms of the agreed goals of the school. If it doesn't fit with our mission don't do it.