Recommended Top Soil depth above clay for Lawn

I decided to get rid of rubble first. After 7h of digging I removed like 12 bircks and 20-30 bigger stones. Easily get through clay and I get 30 cm of nicely moved surface (I was able to gid shouvle with no power used and move it in the ground).

It is all thanks to you... but... There is new issue now. I've moved clay from the bottom and after that when I watered it there is no drainage I think.

I was watering about 10-15 minutes with wide spary but some water has grouped and sink to the ground after around 1-2h wchich I suppose is not impresive. Even when I used 120l of Soild Conditioner and Garden Lime it didnt help...

Do you have any clues/advices, or maybe it is normal ?

Many Thanks...