I load the sleeve on to platen and let the shirt hang. That way I control the off contact better. No collar raising my screen more than I want.
Your post just made me realize that many must be using the same long board that they use for long sleeves. I have always had little shorties for this purpose (as well as odd bags and such), which may change the equation, but, even on my long sleeve boards, the collar clears the board itself.