This approach is fully no-code and will get you pretty far. It effectively simulates a subscription/recurring payment.
Alternatively, you can use a custom approach. The custom approach is to use Javascript or a third-party tool like Make or Zapier to trigger actions in response to Knack events. E.g. Using Make/Zapier/Javascript, you can trigger an action in Stripe when a record is created or form is submitted in Knack.
Designing a workflow around subscriptions can be complex. I recommend experimenting with the no-code approach described above, then if you get stuck you can post your needs on the Expert Network.