Depending on the size of the shirt as to which way below I do it. If I am making the garment I cut out the front embroider it them construct the garment.
I usually turn the shirt inside out and just hold the excess-which is the back of the shirt- out of the way. Of course, you have to sit right there for every stitch but there is no resewing when you are done.
I usually cut the side seam and restitch it afterwards. I also find it easier to work upside down, but watch out if your design has any text in it!
Hoop it and then gather and pin the shirt around the hoop. Pulling the back of the shirt out of the way and rolling excess fabric up. sometimes it is easier to do if you put it on the machine before rolling and pinning. Hope this is clear.