When we need to fold on the belt:
Pull by shoulders;
Turn toward belt while raising high enough that the tail will drag slightly on belt;
Give the shirt a little flick/pop forward, then pull back & down in such a way that the unprinted tail section folds face down, while the the printed section stays face up.
With a little practice, this can be done very quickly & fluidly, practically one motion. You can even add a quick flick with your free fingers to fold the sleeves in on the way down, then use thumbs to fold the neck backward & under as the shirt is landing against the belt. (Good if you have tags that like to curl & crisp in the dryer!)
That said, if you have room to lay flat, that's better - especially for the catcher at the end of the dryer (when you have one). It's way easier to catch & stack quickly when the shirts have been laid flat, and the shoulders are coming out first.
