Hah. I have blocked hours and people will still schedule meetings.

And before you say “Just don’t attend”, I can sometimes use that option. But then other times it becomes all game theory because if they can convince enough other people to attend, you lose politically if people start routing around you on your own project.

Yep, it's a good first line of defense, not a panacea.

At a previous job, we had "no meetings thursdays". It was great for a while, and then product management started scheduling meetings on thursdays "because it's the only time when everyone is free"

No it's not the correct answer.

If it's a meeting of 2-3 people they'll just find time when you're not blocked. If the goal is to schedule meetings back-to-back this might help, but you're not going to avoid any meetings this way.

And if it's a meeting of 5+ people they won't care about your personal schedule, they'll only work around other large meetings, and it's up to you to reschedule your personal things and your one-on-ones.