A slab door is a basic, stripped-down door that doesn't include a frame. When using a slab door, you must attach the door to an existing door frame or create an entirely new frame from scratch, which just adds unnecessary time to your final project timeline. Pre-hung doors are self-contained units that come ready to install, with the door frame and jamb as well as the door itself. The door and the frame should fit seamlessly into the prepare doorway.