g'day peter,

you will need something to lock the blocks together so guessing mortar
will be the go, the base blocks you could mortar to the cement but not
between the block so there is some outlet for water to drain through.

you could create a drain zone under your medium by using rubble or
crushed rock material a layer of 4omm then a layer of 20mm and them
something like cement mix gravel on the top of that and cover with a
double layer of old fly screen or shade cloth to help preven the
medium from clogging this area up. maybe the drainage area could be
app' 1/4 to1/3 the height of a block in depth, assume you mean bessar
blocks or the like?

creat a medium using all sorts of organic material but basically i
would suggest the main ingredient be mushroom compost decomposed or
fresh from the farm no matter try to get hold of any other decomposed
organic material to add in.

len

snipped
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happy gardening
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