pre yawn

ive been singing for a while but have yet to figure out how to sing with an open throat consistently. i would like to know if anyone has suggestions on how to do the  pre yawn before singing. 

It's not necessary to always maintain that position, unless you want that tone specifically! But I find it helps to think backward when singing, and to first practice a song on syllables that make it easier to achieve that openness (like YOH or YAH, for example).