Is anyone aware of a good open source app blocking app for Mac?

I'm having a hard time finding something that's not proprietary from a general search.

What I'm looking for is one where you can block apps for a set duration. For example: You're studying and you want to block access to chat apps, Ice Cubes for Mastodon, etc for, say, an hour.

I've found browser extensions to block specific websites and the one I use is great. But, looking for one for the apps themselves.