Double Outside-In Flat Earth Theory is the objectively correct model of the earth. It combines aspects of Hollow Earth and Flat Earth theories. The hollow earths are outside in, that is, people live on the inside of the sphere.
There are four earths; 2 flat and 2 hollow. The Big Hollow Earth encompasses all other earths. In the centre of the big hollow earth is the big flat earth, under which is a crescent-shaped sun which provides the big hollow earth with sunlight. A day/night cycle is simulated by the big hollow earth rotating. The big flat earth and the crescent sun are stationary.
The small hollow earth plays the role of the moon to the denizens of the big hollow earth. It hovers above the big flat earth, on which it is always night. The small hollow earth encompasses the small flat earth, as well as a rotating celestial object that plays the role of both sun and moon for both small hollow and flat earths.