only way I can think of is to boolean the sphere until it is almost a flat plane. Boolean by the way, is grouping together positive and negative objects. The negative objects become invisible when grouped and cuts out the desired amount of the positive object (dont know if that made any sense). I bet some others here can come up with good ways of doing this, but its the only thing I can think of. If you want more in-depth instructions, just ask and I can attempt to explain. Hope my rambling has helped.