In the FeatureManager design tree, right-click SurfaceCut2 and select Edit Feature.
Click Flip Cut
so the arrow in the graphics area points to the right,
away from the buttons.

Click
.

In the PropertyManager, select Front Plane in the FeatureManager design tree for Selected surface for cut.
Make sure the arrow in the graphics area points upwards to cut away the right button.

Click
.

Save the part as LeftButton.sldprt.