Drawing a shape, but how?

 From:  Franz
8815.1 
It is a positive mold for thermoforming plastics.
I have tried many ways, now I am on this result.
I have connected individual surfaces with network and flat surfaces to form a body.
But the body should look even more "grinded".
Does anyone have a better way to get a seamless surface?
Is there a possibility with the methode of subdivision?

The drawing file is attached.