Some teachers say to swing the clubhead with the hands, others say to swing it with the forearms. I'm now going to suggest a different idea: Swing with the upper arms.
Yes, the upperm arms.
At the address feel that the upper arms are gently pressed toward each other. Feel, too, that they are slightly "closed" to your line-of-aim, the left aiming a mite right of the target and the right more or less straight ahead.
Now swing with the upper arms. The feeling should be that they are swinging on parallel tracks, the right upper arm remaining "inside" the left.
Retain this feeling on the downswing and throughswing. After the ball has gone the tracks cross, but the feeling of having two parallel tracks, one inside the other, will remain well into the follow-through.
The relaxed body will respond to this arm swing while seeming to remain absolutely still until the whole swing is almost finished.
Provided you have a good grip, your hand action can be quite automatic. Don't think of it. Be aware of it -- for one needs to be aware of what the clubface is doing throughout the swing -- but don't think about it.
If it is simplicity you are after, this is the simplest swing there is.