Creating a multi-tenant link shortening application involves utilizing FastAPI, SQLModel, and PropelAuth to manage database interactions, authentication, and user organization. The tutorial guides users through setting up SQLModel for database management, using SQLite for demonstration purposes, and establishing sessions for database queries. It details the creation of models such as a link model that associates links with organizations, ensuring that only members of an organization can access or manage the links. PropelAuth is employed to handle authentication, allowing for user verification and management of access permissions using roles like Owner, Admin, and Member. The tutorial includes setting up routes for creating, retrieving, and deleting links, emphasizing role-based access control and organization membership checks. It also highlights the ease of using FastAPI's OpenAPI support for testing APIs and demonstrates how to handle access tokens for authentication. The guide concludes by encouraging further exploration of the involved technologies to expand the multi-tenant application.