This technique comes from Jim and Linda Eubanks of the Tampa Bay
Chapter.  They used it on their garden railroad, and Marcia and I have
had success with it on our own.

    We all have our own systems for laying track outdoors, and many
systems have been written about in various books and magazines.  Since
we live in Florida, we do not have to worry about "frost heave" and
other cold weather problems that can wreak havoc with our track.  We
also know that any wood put in the ground, will eventually rot, unless
it is pressure treated to be used underwater, which makes it very
    Jim and Linda have come up with a method that is fast and effective
for preparing the right-of-way.  It involves using cement lawn edging
that you can purchase for around 55 to 75 cents apiece.  These pieces
measure approximately  18 inches by 4 inches by 2 inches, and when split
with a chisel, give you two 9 inch sections which will form the base of
your roadbed.
    Once you have laid out where your track is going to go,  take the
pieces of edging and lay them crossways spaced every 16 to 18 inches.
Dig down and bury them in your right of way at the height you want your
track to be. Use a 6 foot carpenters level along the length, and a short
level from side to side to set your grade..  You will find that it is
extremely easy to level these crosspieces in a very short period of
time.  Fill the space between these cross pieces with earth to form your
roadbed foundation.  These support pieces are then overlaid with  roll
roofing material cut to the width of your roadbed.  This material comes
in either tan, gray, or black..  This roll roofing material acts as a
weed barrier, and also looks like ballast on a temporary basis.  Once
you have your track positioned and wired, it can be fastened down to the
blocks using "tapcons" which are available at Home Depot or Lowes.
Remember to leave your track loose before and after your turnouts.
Turnouts need to "float" to work properly. If they are screwed down, or
the track is not loose on either end, the turnouts will bind.  The final
step is to spread loose ballast material over the roadbed. This can be
packed under those areas where the track needs to be raised and
supported.  Remember to keep this material away from the moving parts of
your turnouts.  The roll roofing helps hold some ballast in place, but
to be sure, it can be over sprayed  with a sealer that is commonly used
to seal brick and stone. This idea came from an article on the internet
at the Large Scale Central Web Site.  The stuff is mixed with water and
applied with a garden sprayer.  It dries clear and flat and seems to
hold ballast in place, even when a leaf blower is used to clean off
track debris.  You will have to clean the tops of your rails after this
solution dries, unless you mask your rails with thin masking tape before
spraying.  Some people mix their ballast with mortar mix cement or epoxy
to hold it in place.  I am going to try the sealer, and if it doesn't
work, I will have to try one of these other methods.  I understand
Titebond II glue works fairly well.