My two cents
The base structure of a Service Blueprint shows the customer journey (frontstage) with under it what needs to happen below to create that experience (backstage).
It can be hard to start building out a Service Blueprint, especially for a new service idea you're trying to prototype. In such moments pre-made structures can be pretty useful. Here are a few that you can use to get started:
The classical one
Aware, Join, Use, Develop, Leave. That's the one you learn about in the book "Service Design From Insight to Implementation" by Andy Polaine, Ben Reason & Lavrans Løvlie
The classical one with a twist
I personally like to add a "Re-join" phase at the end of my blueprints to think about the fact that possibility of people coming back to the service and how that might happen. This gives us the following structure: Aware, Join, Use, Develop, Leave, Re-join
One of the first service blueprints I created back in the day.
Marketing funnel + classical one
If you want more details for the aware phase, you can easily zoom in by using the structure of the marketing funnel. Here you can use whatever flavour of funnel that you prefer, for example, the Purchase Funnel, Google Moments. This could give you this structure: Awareness, Desire, Interest, Join, Use, Develop, Leave.