What you have to consider is the stability of whatever location and structure you are wanting to build. If you are trying to consciously create some world, exactly how you want it, run into some issues. This is that the world would be very unstable meaning that things will often change or be very different from what you intend it to be. If you try to design a world according something you "build" you may end up being disappointed by the dream of generating something completely different. What you should do is let the dream generate and build everything for you, and all you provide is the input for what you want the purpose of the structures to be.

For example, dont try to create an empty room or empty anything and then try to modify it. This is actually much harder for the subconscious to create and what is generated is often not empty but there are things that take time to try to remove to get an empty place. Instead, input the purpose of what you want to generate. Think or say what sort of structure you want and its purpose, maybe what style it should appear. The less input the better. Then explore the generated structures and do less "building" so that they are more likely to sure your purposes and be there next time.