Your slabs should still be working. You may just have to
work the slab more.
There are numerous different ways to work the slab. Some of the techniques may work better at different tiimes of the year.
_Straight down drops and just letting it sit on the bottom. (Usually good for inactive fish)
_Straight down drops and barely lifting it off the bottom and simply holding it there. (Usually good for inactive fish on the bottom that want the bait off the bottom. - Think of dropping it in their mouth.
)
_Straight down drops and quikly lifting it 2-3' off the bottom and then lowering the bait on a tight line controlling the fall. (This is good for fish that are on or near the bottom and are conducive to being active.
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_Striaght down drops and quickly lifting it 2-5' and letting it free fall down back to the bottom. (Make sure you know by line resistance where the bottom is. If you get slack line before it hits bottom - fish on. This is good for actively feeding fish that are in the lower part of the water column.)
_Cast out and let it fall to the bottom. Lift the rod and let it fall. Think of working a jig'n pig faster. (This is good for those fish that want the bait moving horizontally rather than just vertically.)
_Cast out and let it fall to the bottom. Just a slow reel enough to keep the slab off the bottom with a few pauses to make sure that you are "in contact" with the bottom. (This is good for those inactive fish that want the bait moving horizontally.)
_Cast out and let it fall to the bottom. Rip it off the bottom and either let it free fall back to the bottom or tight line it back down. (Good for actively feeding fish.)
_Cast out and use a count down method to get the bait to a depth where fish are suspended. Work the bait back as if you are horizontal jigging it. (Good for suspended fish in a tight area.)
That's all I can think of right now. I'm sure there are more. But one of those techniques should get your slab bit at some point during the year. Sometimes you have to use more than one technique within a cast to get the fish to bite. Just have to experiment.
Good Luck and hope that helps a little bit.