I'm looking to build units either side of my fireplace. I've never had anything like that built and I've never seen how they're built so excuse the stupid question - but are they built in the same way a kitchen would be built? i.e. carcasses assembled, doors put on, and then surface on top of it? Or does it need building from scratch? Just in the way of an example, here's something similar to what I'm going to be constructing - fireplace with units fitted to each side exactly. So I'd expect cabinets would fill most of the space with a spacer piece for where it didn't match exactly? Am I on the right lines here?