We'll usually start with an Abstract which is basically a starter to get your teams thinking about what kind of solutions we can provide you with.
Many of these are based on real world projects, so will probably be very relevant. Here's an example for a Shop selling products. There's others here.
This is a minimum viable abstraction whereby relationships between entities in the system are modelled according to their cardinality.1
For those interested, this diagram is dynamically generated in the browser as SVG using Web Assembly.
[1] Cardinality defines the possible number of occurrences in one entity which is associated with the number of occurrences in another.