Is there any danger slicing pickles hours before frying them? I am frying pickles later tonight, and I would like to pre-cut all my slices to fry. Is there any reason I shouldn't cut them then put them back in the jar for later?
No, there is no danger.

Just slice the pickles then put them back in the jar or alternatively wrap them in foil and place them back in the refrigerator until you need them.