Stripe Free Trials
Setting up free trials in Stripe or Stripe Checkout
Subscriptions
To add a free trial to a Subscription, navigate to Billing...Subscriptions...Create subscription
In the *Create a Subscription modal, enter the number of days for your free trial.
Using Stripe's API
Free trials can be added to a Subscription through Stripe's API. See Stripe's pre-built Checkout page for an example.
Stripe's full trial documentation can be found here.