Treat people like adults, not children. Don't babysit them, micromanage or track what they're doing every minute of the day. If they turn up late or leave early, let them if they've done what you need them to do. If they walk out of a meeting because there's no reason for them to be there, let them. Treat them like adults, they presumably know what they need to complete their required tasks.

Hire the right amount of people for the amount of work you have. Don't overburden them and don't have them so bored they want to poke their eyes out.

Video games, parties etc are all well and good but are essentially meaningless. Employees did well? Give them the one thing that they can't get back; time. Give them an afternoon off, let them go home early.

Don't force "fun" or bullshit initiatives on them if they're not interested. Accept that many people simply want to do their job and go home. For a lot of people it will be "just a job", not something they define themselves by. And if they're doing what you need them to do, that should be OK.