I've lived abroad a lot, and also moved cities within the UK frequently, so I do keep having to make new friend groups.
I go to social groups of things I'm interested in (rock climbing, social dancing, board games), chat to people for the first few times, then start asking people that seem interesting and that I want to get to know better out for coffee 121.
If they say no, I don't take it personally, cos they don't know me.
If they say yes, great, and some of those turn into friendships, whereas some you discover you don't have enough in common or conversation doesn't flow, so just let it tail off, and no big deal as no one is very invested at that point.
Once I've met people a few times, then I usually start getting invited to things, and start inviting them over for dinner, to do the hobby, or something else social like a walk, cycle, comedy night, quiz, low key gig etc.
And a step on from that, they start inviting me out with others/I meet their friend groups etc, so then there are more people who I get to know and might like to form more friendships with.
But then a) I like hosting, b) I like meeting new people and c) I don't get invested until I know people quite well, so I don't have any fear of rejection etc, which makes it all low stakes and easy.
I'd still reckon I only make friends with about 1 in 15 of the people I go out for initial coffees with, maybe even fewer, so it is a question of making an effort and meeting lots of people.
Plus, depends what you mean by friends - I have tons of "hang out with, social friends", a reasonable number of "reasonably intimate talk about & share things about our lives" friends, and about 8 really close friends who I could call at 3am or say "I need to sleep on your sofa for a month cos something in my life exploded"
I think it also helps that I don't have kids so I have more free time than most parents would do...