Fred Perrin does a variation on the IWB- he uses a thick braided lanyard, and a "leash" attached to the bottom of the sheath. The leash is attached to your belt/beltloop,and the knife is tucked down the side of your pants, with the lanyard hanging out. Draw is basically running your thumb along your waistline, until you feel the lanyard, thumb and index fingers colse on the lanyard, and jerk upwards. The fingers close around the grip, as it comes out of your pants. Removal from the sheath is accomplished by reaching the end of the leash. Works best with blades 4" or less.
I've played with this;but my overall preference is grip "out" carry,IWB. This would be a good totally out-of-sight method,though.
I believe pics are either on Don Rearic's site,or at the Perrin link from there.