Select one or more objects on the artboard, and choose Object > Slice > Make.
Select the Slice tool and
drag over the area where you want to create a slice. Shift-drag
to constrain the slice to a square. Alt‑drag (Windows) or Option-drag
(Mac OS) to draw from the center.
Select one or more objects on the artboard, and choose Object > Slice > Create From Selection.
Place guides where you want to slice the artwork, and choose Object > Slice > Create From Guides.
Select an existing slice, and choose Object > Slice > Duplicate Slice.