They come in two styles. Cut, which mounts strait to the engine bolts and Yes, you have to cut the fairing, and No-Cuts which usually us a bracket that bolts the the engine bolt and shifts the actuall slider to a point where there is no fairing..
Unfortunatly, many No-cut sliders can slip and shift under the force of a slide and damage fairings and frame anyway.
If you're good with a dremel, it's not hard to do it yourself. Mondo had his mounted by a local shop for not too much $$ so that's an option as well. I'd recommend the Cut sliders.