If you need a method, work together. It seems as though this site has an international group of users. If, together, you could note down the time and angle of sunset, and the position of the Sun elsewhere at that time, you could work out relative distances with a universal landmark.
From that you can work out the relative locations of the areas of the world: that would find a map no matter the world's shape, and nothing there could be altered.
Does the user group of this site want to attempt this?