There have been some interesting ideas about screened bottom boards lately.

Here is what I do:

I fold a sheet of 1/8 mesh on the bottom of the lowest hive body with one or
two inches of extra material to fold up along the sides and staple all around
(using t-25 wire staple gun.)

two paralell cuts about 3 inches apart and 6 inches long are added at the
front end in the center. This forms a peice that can be bent down to form an
entrance ramp for the bees. It also can be bent back up and stapled to seal
the hive for moving.

The entire mesh can be removed and restapled for reversing etc. No bottom
board is used at all.

The hive is set on an old AUTOMOBILE TIRE for a stand. The tire has a hole
drilled into the sidewall on the ground for water drainage. The tire is
cheaper than free, gets the hive off the ground, will not rot and allows
enough room for mite drop and ventilation.

Cesar Flores
Colorado USA