The directions are to fold the hood doubled and join the cast on edge to form the back seam of the hood. But the cast on edge and the cast off edge are basically equivalent, each are rows of garter st. So, you could switch them and for a neat and fairly invisible seam, you could take out the cast off that you've just finished, fold the hood and do a 3 needle bind off on the live sts to join the cast off edge. That will be the back seam and the cast on edge will frame your face.
If you'd like directions for the 3 needle bind off (and it's a great technique), go to the Free Videos tab at the top of this page, Tips, Seams, 3needle bind off.