Stacking the LR?

Or aquascaping, whichever it's called.

I apologize in advance if this has already been addressed. I swear, I actually look through the posts to see if my questions have been addressed already.

So, I know I need a couple of larger size rock, then medium i'm assuming. But then how to I stack them? Do I glued them together, or just set them on top of each other? Is there a method to the madness or...?