Some people have kinda touched on this but at it’s simplest….

Show up to the same place at a regular time that other people regularly show up.

Being around the same people tends to be how friendships occur. You naturally just kinda do it as your regularly around them. When we’re young this happens automatically at school. As adults it can happen at work but coworkers are often in diff stages of life so it’s more of a hurdle. Granted plenty of my friend are past/current coworkers.

The simplest way is some sort of sport, activity, club etc. like you’ll inevitably make friends with people on a sports team you play on.

If you go to the same gym every Tuesday, others will be there and friendships may follow. Yes takes a bit more active effort there but still.

Same with I’m sure volunteering places etc.

A shared regular activity is the easiest way to make friends.