A question about slabs.... If one were to use a loose bonsai soil mix on a slab planting, what prevents the soil from spilling over the side when watering? Most of the time I see moss applied which I assume can help, but then do you keep the moss on year around on slab plantings? If so, how do you keep the moss alive if the trees require lots of sun? So many questions....
Edited this post because I found an answer. Also, I hope this is not considered "hijacking a thread"!
Anyway, the info is here for anyone who may have asked the question.
http://forum.bonsaitalk.com/showthread.php?t=10600