You can place your car into neutral when sliding on ice but there's no need to put your car into neutral when sliding on ice unless you have a manual transmission.
If your car is a manual transmission then you would want to place the car into neutral and then remove your foot from the clutch so you don't have to hold the clutch pedal down.
But with an automatic placing your car into neutral when sliding on ice will do nothing to help the situation because when you remove your foot from the gas pedal the cars engine will still run while the transmission doesn't move the car.
When you begin sliding on ice keep your hands on the steering wheel and try to get off the road safely but do not slam on the brakes just lightly tap the brakes and try to keep control of the vehicle and if you have to steer the car into the ditch away from oncoming traffic then do so even if hurts you a little or damages your car.
When your car stops skidding on the highway or roadway then you can slowly accelerate to hopefully get going again but if it's not safe then try to pull off on the side of the road and stay there until it clears or you can get help.