Ways to offer free testing periods

Hi, 
Hope everyone's doing well!
I've trouble understanding how can I offer free subscriptions to certain users (sometimes, I want to give them a free overview of the product, that I can cut later on).

I didn't find a way to do this through Jumpstart admin (creating a subscription, assigning it to an account, etc). I'm starting to create rakes - but it triggers weird behaviour on other parts of the platform (Billing changes, etc.)

What's the best way to handle this (ie. free subscriptions that we can manually change in the admin) ?

Thank you! 🙏