You certainly don't want to seal them up completely. You won't get any
spalting formation that way. If it's already spalted then sealing it up
will halt the decay processes and let it dry. That's good but it won't let
any fungus in there otherwise.

Stand the wood on end (endgrain down to the ground) and seal the top
endgrain. It's best if you'll have some organic matter (leaves, manure,
non-sterile earth) under the wood in order to increase the chances that the
right kind of fungus is present to do the spalting in the first place. No
guarantee that you'll have the right environmental conditions or that you've
got the right kind of White Rot fungus to do the spalting but at least
you're giving it a chance this way.

- Andrew

random patterns that are quite striking and beautiful. Completely seal
some
pieces with anchorseal and wait. You may be very pleasantly surprised!

-Jim Gott-
San Jose, CA