Best practice for order flow

I have a couple of services that I would like to sell, and when a customer chooses a service, they can choose from optional physical products (such as a mug, a poster, a hat, etc.).

For my commerce site, I think I would prefer to have something that is more wizard-like with a fixed order flow:

1. Choose a service
2. Choose from zero or more optional physical products
3. Go to the payment page and checkout

So it's less a storefront and picking random items to put in a shopping cart, and more of a fixed order path with specific services or products on each page.

At the same time, the physical products are the same for each of the services, so I'm trying to avoid tying them directly to each service (a mug is a mug and costs the same, no matter the service selected).

Are there any best practices or recommendations for something like this?

Hi,

Did you find out any more about this topic? I'm trying to implement a product configuration gizmo within Squarespace and I'm drawing a blank at the moment.

cheers,
-tomek