It just depends, what size crappie are you calling a "Monster Slab"? If your looking for a chance to catch 12"-14" fish, Geist would be the lake that seems to be giving up the most of them currently. The launching ramp is located a little south of 116th and Olio Road.There are a couple of other lakes, Eagle Creek and Morse. I have not been to Eagle Creek for quite some time, but Morse is still on the upswing but not giving up as many good ones as Geist.
Hope this helps and good luck!