The hard part is most houses do not contain a single plumb, true, and square room. Walls do weird things, especially where they meet floors and ceilings. Floors are hard to get flat. Etc. I'd say once you resolve all this and get your rail level and parallel to the floor, yes, then throwing up the cabinets is the easiest part. After that, you probably want to learn how to do some molding to trim them in.