How to create a gravel garden yourself if there is no basement?

As far as I understand, the 80cm depth comes from the fact that infiltration can easily take place down to frost-free depth. Otherwise, it can freeze in winter, which prevents further drainage and can cause damage. How relevant this really is in practice, I don't know. You. is definitely not the first to question this.

We also don't have a basement and will make an approximately 20cm gravel bed. However, we have a generous roof overhang, so it only rains a bit more intensely on one side. The rest basically always stays dry.