I tend to use the tool of terrain painting for marking where I want things to go, roughly. then I modify the terrain if I want, first roughly and then I smooth it out, then I build the shell of the house, add stairs / make ramps with the terrain tool to access the house. At the end I do all the decoration and furnishing room by room. Lastly, I remove all the terrain paint I had for markingsa nd add new terrain paint for decoration (I think it makes a big difference). By this point I'm usually broke so I decorate the garden with default items.