Why does coconut oil solidify into a hexagonal pattern

"This coconut oil melted during a heat wave and later re-solidified. Why did it form this honeycomb structure?" asked pensive badger on the askscience subreddit. Many answers have been given, using science-y words like "Voronoi diagram," "dissipative structure," "Bi(C)nard cells," "Rayleigh number," and "crystal nucleation." What is the answer?