There's an ol' saying, "draw it first - then carve it". Some folks even say, "if you can draw it, you can carve it". I'm not one of those. I am one who thinks that it is a big help to practice drawing faces. I do it all the time. And I can see an improvement in my carving.
With a paper and pencil, just draw some Santa faces. Try to make them happy faces/expressions.
I keep a pad of paper and a pencil by the telephone just for that purpose. Comes in handy when I'm on the phone for a long period of time doing more listening than talking. In the above example, notice that most drawing were somewhat happy. What makes them appear happy? A smiling mouth, round fat cheeks, big round nose! Now, just transfer that to carving the face.