Constructing slabs

Hi Everyone, 

This is my first post here and I have to say that this forum is an amazing resource; Ive been playing with GH for a while now and cant stop. 

Im trying to construct a a massing model for a project at work and cant seem to work out how to start.  

on the top right you can see what I want to archive and ive done that manually but id like to be able to control things such as slab height and more importantly angle of turn  and lenght with GH. 

Any suggestions? 

Thanks in advance.