There is no set way to build your reef, but it is important to make sure it is stable. You can help that by using plastic cable ties to tie the rocks together to keep them from falling. I don't think it's good to stack the rock against the back glass. It makes it a little tougher to stack it, but you need to try to keep the reef as open as possible. With it away from the glass, you can put a power head behind the reef, which will help with keeping detritus from settling. Don't build a brick wall! See the book "The Modern Coral Reef Aquarium" by Nilson and Fossa for some interesting ideas for building over-hangs and odd shapes in your reef.
Sonny