Slack is a pretty good way to communicate with others.
A few ideas about how to optimize use of Slack:
When starting a project, create a private channel for that project. The benefit of a private channel, rather than a conversation with the collaborators on this project is that you can then invite additional collaborators on the project to join the channel as the project evolves. This can be a homebase to post developments to the project: figures, questions that arise, and technical questions.