Workflow for user uploading a file - system link to storage folder

I'm working on a legacy Zend Framework 2 application, and I managed to convince my boss to use Envoyer as the deploy platform. I saw the Laracasts and read about 6 threads that explains the system link with the default/storage directory.

However, I'm still unsure of what's the workflow on the system link. Suppose you have a running application (different server) and you're doing a new deployment in order to fully migrate. So what are the steps?

1. Configure a post deployment hook to link default/{{release}}/public/data/ (this is my upload folder) to default/data
2. Copy/Paste the most recent backup of my data folder into default/data
3. Deploy application
4. When user uploads new data through the web app, it saves the file to...?? <--- HERE, where? directly to default/data ?

Note: I'm new to Envoyer (used Forge in the past, loved it) and I'd love a detailed explanation of this, so that I can explain my boss the easiest way possible, so that he feels as confortable as I do with Taylor products like Envoyer.

Edit: I'd also love to avoid solutions that include changing the source code to upload files outside of the project root, since, as I said, we're working with a legacy application, no SOLID code found, no tests, we can't really guarantee changing a path won't break the system. Also my boss won't like the idea of changing the software to work with a service, rather the service being configurable to work with the software. Thanks, once again.