Recently, I wrote an article about building earthen floors for Green Building Elements. Earthen floors are commonplace in straw bale and cob buildings, but they can also be installed in more typical suburban homes.
Check out the full article here: Natural Building 101: How to build an earthen or adobe floor.

[...] After that, I’ll plaster the walls, and finally, I’ll install the top layer of the earthen floor. (It doesn’t make sense to complete the floor before the other dirty work is [...]
Always lay the floor last so many people do it first then end up damaging it whilst completing the other works.