Also: “work out the complete shot, first.” Is the camera going to remain stationary the entire time, or might you “cut” to various points-of-view? To keep the pace up, are we going to actually see every slice being cut, or might we instead CUT TO a shot in which several slices are already cut and lying next to the knife? It’s up to you, but the difference matters in what you do next to actually realize the shot that you’ve envisioned.
You can “block the whole thing out” with by cutting the lemon shape into a series of cylinders, one per slice, and keyframing the movement of each slice. A thin rectangular plane can serve as the knife-blade. Using your powers of human imagination and visualization, block-out the shot or series of shots that will depict the lemon being sliced and whatever else you then want to do with the slices. (Want juicy drops? A tiny sphere can stand-in for the drops.)
Once you have finally agreed-with yourself about how the shot will “go,” you now know exactly what you need to be able to animate. Model, rig, and animate that. (In other words, don’t “first rig everything, then figure out how you intend to use it.”)