Well, the way I’m trying to say doesn’t involve booleans. The topology, with the loops and all, has to conform around the smile shape. In your pictures the smile geometry is just floating separate to the plane. Something like this:

Which is all wrong, because the topology around the holes doesn’t have the supporting loops. You need to aim for something like this:


Those hole are well integrated in the geometry. You model that flat, that when when you bend your shape, the loops already support the surrounding geometry:

All of that is just to avoid having to model the smile while the curvature is already there. It is a nightmare to model something in a curved shape. That is why you model first flat, and then you curve.
I guess the course that mostly does something like that is JL modeling the cookie:
https://cgcookie.com/lessons/modeling-a-logo-pt-1-0ca5d2b8ee804f38