Guidance please - starting to build NAS scape

[GuppyHJD]

It's time for me to start gluing my scape together but I am having a mind block.
Do I use a larger flat sided piece for the bottom and plan for it to sit on the tank bottom and sand around it
OR
Do I use several small chunks of rock to raise the flat bottom piece up 1 1/2" so creatures can clean up the structure?

Any suggestions or recommendations?

Thank you

 

[Idoc]

I prefer the rock flat on the glass with sand around it.

 

[Jedi1199]

I did the flat rock on the bottom with mine

And since he photobombed all of these shots... here is the showoff...

 

[GuppyHJD]

I prefer the rock flat on the glass with sand around it.

Thank you