I mostly just focus on trying to find one or two people who like pairing and always suggest to do it with them. I always aim to be positive, anti judgemental, understanding, curious, etc. so theyll feel comfortable.

One of my coworkers in an old company set up a "slack" watercooler channel he would always pair in with an explicit invitation that anybody who wanted to drop in could at any time, even if it was just for a chat. That was cool.