No, it isn't explained in the FAQ. We all understand half the earth is lit up at a time by the sun, right, this is easy to understand with a round earth, but a flat earth? You would need a half-circle of light to be cast upon half the flat earth. More than that, you would need the edges of the half-circle to bend nearly 90 degrees, to give the appearance of sunset/sunrise. More than THAT, you would need the southernmost countries (closer to the icewall, such as New Zealand) to have a much larger stretch of sunlight to match the smaller area of northern countries, i.e britain etc.
A half circle of light. No.