Your drawing looks like you want to put a horizontal glass, (or similar), shelf across one end of your tank at a certain depth with the tank filled to roughly the level of the shelf.
Sure, if that is what you want. Well cut piece of glass, tube of aquarium grade silicon sealant, few stand off pillars while it sets.
Without more detail it is difficult to comment. I can see cleaning issues with the covered portion. The substrate on the raised portion will need containing as it will tend to fall over the edge.
I guess the question is what are you planning here?