Tables for Slack Clone
Let's get started by looking at the data model.
The primary functionality of the app revolves around users and their messages.
So we have the following tables.
Slack app has workspaces where users can join. It is managed by the owner and the admins of the workspace. The following tables takes care of this requirement.
Each workspace can have channels scoped to a specific topic of discussion having subset of members from the workspace. Members of the channel can post messages to the channel that everyone can see.
The final model roughly looks like the following with basic relational columns:
Note that it doesn't have the detailed column list, but it should give an idea of the relationships between different entities.