Assuming you can see bits of the ground it's a lot easier to navigate when you are at 10,000'. And as you go higher, it becomes even easier. There was no controlled airspace and no doubt barrage balloons showed you where the biggest cities were. Now assuming pilots were like they are today, they either knew where home was (one village west of the first bridge over the river sort of thing), carried a crib sheet, guessed or landed at the wrong place and got directions... Or just followed their colleagues.
PM