Source of truth document
Thought experiment: if you were randomly asked by the CEO about one of your initiatives, what document would you send to get them up to speed?
A lot of conversation can happen on Slack and video calls, decisions are made, and context is gathered, so it's important to keep a source of truth document that you can refer to, and share if needed.
Don't make this document a heavy read - write what's important for the project, detailed information should have their own documents that are linked (e.g. forecast models, detailed technical design documents).