A visitor buys a pass or intro offer from your booking page by typing an email and paying. No account to create first, and nothing to set up afterwards: the receipt is their way back in.
Prerequisites
On a pass or intro offer, the last step before payment asks one thing: "Where should we send it?" They choose Continue with Google, or type an email and press Continue to payment. There is no "sign in or continue as guest" choice and no name to type; the name comes from the card form.
They land on a page that says what they paid and that the pass is active, with a "Book a class with it" button. On the device they paid from, someone whose email is new to Klasly is signed in straight away. They get one email: a receipt with a "Book a class" button and a line telling them to enter that email on your sign-in page for a code on any other device.
The buyer is added to Members when the payment succeeds, with the pass attached. Someone who opens the checkout and leaves without paying is not added.
Open Settings → Widget and switch off "Buy with just an email". Visitors then confirm their email with a code (or Google) before the payment page opens. It is on by default.