Very simple. Under object menu select 'New Drop Zone'. It will be added to your current group. Make sure it is selected in the layers panel. Hold the shift key down and grab any corner and resize to your liking. The shift key will retain the aspect ratio. Then drag it where you want in the canvas. If you want it to rotate add the spin behavior from Behaviors>Basic Motion in the tool bar. Go to inspector>behaviors tab and set the rotation axis/speed etc.
I forgot to add that if you want the drop zones to be active in FCP i.e. add clips to them in FCP, then I would start with a motion generator template. After you'e finished then choose save as from the file menu and click publish in the window after making your choices in the pop-up menus. The generator will show up in the generators browser in FCP with the namae you gave it.