‘Table of rows’ in SQL Databases equivalent to ‘Collection of documents’ in MongoDB. And Star Data Model can be represented as document with nested properties, like this:
To put simply, your fact document will contain dimension documents as nested objects.
With this structure, you will not need to use any joins ($lookups), because every dimension is already joined to the fact data.
This scheme will be a perfect fit, only if the total size of such document will not exceed 16MB.
Check this OracleDB and MongoDB Comparison for more detailed overview.