I wouldn't start with lines.
if ur not trying to replicate the piece but rather produce something similar of ur own, I would expand the canvas to fit the whole head.
rough in the head, eyes mouth etc using colour and a few circles and things which will be painted over later.
even just follow some tutorial on youtube u will get a decent result.
u can even cheat by drawing it upright and rotating, its not a bad idea.
use photo references of uncovered faces until ur happy with the layout.
it doesnt need to look pretty or shaded, things just need to be in the right place.
then just paint in detail the area of the focus and crop the image later.
u can even add a layer with a black border that shows the area ur keeping but allows u to take a glance at the rest when u want.
oh and I encourage u to save ur progress as u go and post ur successes and failures, they're all part of the process.