Lack of drainage in border

[LordsAppellant]

Hi

Just cleared loads of stones from this border. Although it surrounds a patio, it was previously part of a lawn. Wanted to put some flowers in, so dug down to about 20-25cms depth. However, I then hit a load of concrete, and this area did not drain after recent heavy rain.

Am I wasting my time adding soil/compost/manure in this scenario?

Thank you.