In a Flat Arc, the Normal World can manifest in two ways, the first of which is as a good place that represents the character’s Truth. In this instance, the Normal World will either be destroyed at the First Plot Point, or, more likely, the character will be forced to journey away from it in order to protect it.
The second possible manifestation of the Normal World is as a less-than-satisfactory place, which has been cursed by a great Lie—against which the protagonist’s Truth will stand in direct opposition. The protagonist will use his Truth to destroy this evil world and build a better one in its place