I remember reading once that the biggest predictor of friendship/relationships was physical proximity. And a book about a spy who built a relationship with and turned a diplomat by appearing at/around the same grocery store repeatedly, gradually building familiarity then trust.

I often think about these examples. And as much as hobbies etc are good ideas, I think one could start even simpler - walk the dog at the same time every day. Or drive to get a coffee, hang out there for 30 mins, etc. I find a change of scenery helps me too, as well as a routine, to lift the spirits, and those chance encounters will repeat.