Neck shaping

I am ready to shape a neck line and am a bit confused.

RS:Work 16 sts, work next 17 sts and place on holder, join another ball of yarn and work to end of row.Work both sides at once to piece measures 16 inches.

I know how to add yarn and how to work both sides. But if I work the stitches to put on holder, isn’t the yarn going to be on those stiches when I turn the work. How can I use that yarn to work that side without passing it over the held stitches? Can I just slip the stiches onto the holder without working them to continue working that side?

Maybe there is a reason you need to work those center stitches. Just do what it says, but join a new ball to the first side to work it instead of joining the new ball where it says to.