Making and sinking some BRUSH PILES!
It is not hard to do and you will have a location that others will not know about. You need to think about what kind of wood and what kind of location.
As for the wood. Some wood last longer in the water longer than others. Cedar, walnut and hickory are some of the longest lasting wood. As for location. Place the brush NEAR a good crappie location, but not so near that others will stumble on it. Remember some states have regulation regarding brush pile installations (if that would stop you any way:D ). The brush pile does not need to be real big to hold lots of crappie. Like on the lake I guided every one fishes visible brush but never seem to locate submerged brush.