1. Collect new employee contact information and personal data
2. Request for an initial access for the new employee and provide him/her with a list of requirable accesses (personal account and similar) to retrieve on his/her own
3. Introduce he/she to a team, make acquaintance with staff in charge, add to chats, meetings and mailing lists
4. Give an overview of the company/team/project
5. Assign a mentor for a new employee
6. Provide an entry point to a project wiki, onboarding program or any
7. Set up the nearest tasks and midterm plan
8. Schedule a training/(s)

All stuff like: description of the project, architecture, modules, not obvious solutions, installation process, CI/CD pipelines, branching strategies, environment(s), description of how to contribute and how to use the project, - should be in your project wiki.