Toggle between Slice tool and Slice Selection tool

Control

Command

Draw square slice

Shift-drag

Shift-drag

Draw from center outward

Alt-drag

Option-drag

Draw square slice from center outward

Shift + Alt-drag

Shift + Option-drag

Reposition slice while creating slice

Spacebar-drag

Spacebar-drag

Open context-sensitive menu

Right-click slice

Control-click slice