In article , Uncle Marvo
writes
addendum ...

is it possible to make the floor of the greenhouse slope, even a little bit?

I'm afraid not. However, the door flew away for the second time in a
bad storm, it left the broken glass behind. We retrieved it and it is
now fitted with clear plastic where the glass was. It should be
possible to make some air holes at the bottom of the plastic.

--
Judith Lea