Adding attachments to an item that does not yet exist

I am looking to build some functionality where users enter info about a Job (model) and can add attachments to that Job before pressing the submit button.

In terms of relationships, the Job and Attachment are always one-to-many.

The issue is when I upload a file I want to be able to attach it using job_id, but that job doesnt exist until the submit process is complete (after uploading the docs).

My current thought is to create the relationship as a many-to-many with an intermediate mapping table. That way I can load Attachments and then link them to the newly created Job on the submit process.

Is there a better way to handle this?