[Cob] Earthen Floor Question

[b]

I want to share a question posed by a friend of mine.  I have never done the earthen floor in this order but find it interesting.  I can see a few possible objections depending upon local weather conditions, but still . . .

Comments please.  Thanks

Preston of the Mojave

 . . /I am in the planning stages of yet another straw bale home  
and looking for input .
I have done earthen floors before in small structures , placing the 
materials  after all the
interior wall mud .  Basically , it has been the last item on the 
agenda.

I am wondering if you have any experience or know of any one who does 
in creating the floor
at the first stages of building much as one would do a cement slab on 
grade , inside of the
perimeter footing ? In previous  buildings, I have left the pour until 
last thinking that it would  be
quite difficult to protect   during the construction process .  I have 
experienced that even concrete
floors  suffer  under the rigors of building and are problematic to 
restore to original beauty.
I have thought that perhaps it might be workable to place  an initial 
layer  as a clean working
surface  at the outset --protect it with 6 mil. poly and flakeboard 
during the remainder of the
building and then add on the final lift of floor material at the end.  
In this fashion one would
have a stable , flat, clean surface to work on  which would certainly 
make life easier than
laboring on the dusty and relatively uneven  surface of  a compacted 
sub base.

I would very much appreciate your comments and speculations.  Please , 
feel free to pass this
query  along to any one that you think might be of help in this 
situation.
/ . . .