If you only need a wall to cover the existing wall without any other requirements, follow the existing wall with the passport; the point that is "furthest in" the house is your guideline. Attach a floor plate about ten/twenty millimeters further into the house and level up with a standing stud, then attach the top plate to the ceiling. Then you'll have two tracks you can frame however you want. Note: don't forget the angle and measurement against the opposite wall.
Hope this helped a little.
/ Just me.