I found working with juniors _fun_ and rewarding in person. Remote i have hated it and don't think I've been good at it
One of the biggest skills you're helping a junior to learn is how to break apart a big task into small, workable components. Maybe they are assigned a user story, but that user story is going to need multiple functions written, or something like that. So you might start with pseudo-coding or creating the interfaces together, talk high level about how a particular method should work, and then let them do that part by themself. "Let me know if you get stuck or done with that and then let's do a little informal code review."
Beyond that it's the normal management stuff of compliment sandwich on negative feedback, etc. The normal things you do to build and maintain rapport with coworkers.
It's true that the barrier is a bit higher remote, but it's not unsurpassable.
That being said, with the former culture, it's harder to ask question online and asynchronously, since usually they prefer and wait to have in face session instead.