Why, in Lord Of The Flies, does the author spend so much time explaining exactly what the meeting place looks like?

William Golding provides a detailed description of the meeting place in chapter one. The purpose is to convey to the reader its significance in the scheme of things. It will acquire a profound status because it is the place where the most important decisions will be made. It is central to the development of the plot and has to, both literally and figuratively, be dominant, admired and respected. In a physical sense, it should also be easily identifiable so that the boys would know exactly where it is.
In addition, by closely describing what it looks like, Golding deliberately gives the meeting place an almost iconic status. The fact that its location abruptly interrupts the beach with its 'square motif' creates a clear demarcation from the pleasure of being on the beach to the rigidity and formality associated with that of a meeting place. The fact that it is square alludes to the school quad in which schoolchildren are brought together for meetings. This, in itself, makes it a proper location for meetings - a place the boys can identify with.
Golding also describes it as a platform, an obvious indication that it is an ideal place from which announcements can be made and meetings can be called. A platform is generally seen as a place of importance from which one can address an audience. Its uncompromising nature further emphasizes its significance as a place where serious matters have to be resolved.
Further in his descriptions, Golding illustrates how convenient the area is for meetings. Its surface is covered with coarse grass - perfect to sit on. Added to that, the palm trees which had fallen down in criss-cross patterns, create convenient seats for the boys to occupy during meetings. In addition, the low-growing palm trees with their large leaves provide excellent shade.
Furthermore, because of its dominant position, the platform also offers an extended and beautiful view of the beach, the lagoon and beyond, and will make it easy to perceive the approach of others, as Ralph and Piggy do when they witness the arrival of the other boys. 
All in all, Golding presents the area as the perfect place in which to hold meetings. Faced with such natural perfection, one would assume that the boys would be grateful and respect what they have by exercising due diligence and behave civilly. This, ironically, does not happen. The promise held by the meeting place, so profoundly flawless, is shattered when everything falls apart when the boys are gradually driven and eventually overwhelmed by their innate desire to destroy.