Food is almost always photographed using soft shadows (the softer, usually the better). I wanted the slice's shadow to connect in the mind's eye the slice with the whole avocado and to complement the angular, defined lines of the slice itself. Using a soft shadow would not have accomplished either goal, so this photo is a good example of why it's always a good idea to think of common concepts as guidelines rather than rules.
I learned while making this photo how to achieve an even, clean slice of avocado that is ideal for that pristine style of photography: use an avocado that is not yet ripe.
Setup
The tabletop and background are a single sheet of green art paper. A flashlight, which is flagged by gaffer's tape attached to the lamp, is on the right side behind the avocado. It lights the top of the slice, the avocado that is whole and the tabletop. It also lights the background to make it relatively bright behind the whole avocado. Another flashlight on the right but in front of the scene lights a white reflector on the left side of the scene. That reflector brightens the front of the slice.