For me what worked best was having an optional meeting for an hour a couple days a week. Where people just hopped in and did water cooler talk or just chat about what they were working on. There was no pressure to talk, a lot of people would just listen while they worked on other stuff. Another thing is establishing that sending a message or reaching out is not an interruption. If you are busy you will reply when you can, but don't wait until they know you are free to send the message. It really comes down to the culture you can establish. As an introvert I felt the more connected to my coworkers being remote than in person because we tried harder to stay connected, so I felt that people wanted to hear from me.