as no one has responded to this one yet , Ill give it a go
this is what I used
eggcrate -----got mine from pond supplies
acrylic rod or acrylic tube-- clear plastic got mine from clear plastic supplies uk
aquascape construction epoxy -----local lfs
and a saw
I cut my eggcrate to the size I wanted , cut six legs out of the acylic rod for each length of eggcrate
marked the cross section, of the eggcrate on top of the rod,and also the depth,of the eggcrate cut it and pushed them into place, filled in any discrepency of the cut ,with the epoxy .made sure it stood firmly with no shaking at all .
placed one in the tank, with a piece of live rock on it then placed more rock to my taste
sorry the pictures dont show a lot but its the best I can do
this is with one piece of eggcrate
all underneath the eggcrate is empty with a powerhead eitherside for waterflow , the fish go under there regularly and seem to like it .
some friends have done the easier option of putting a number of wineglasses
underneath the eggcrate and putting the rock on top that works fine for them as well

hope this is of some help
