When you first learn about mandalas, you learn about sand paintings:
But in the Guhyagarbha tantra, outlined in Luminous Essence: A Guide to the Guhyagarbha Tantra, it is said:
The subject matter of this tantra is the maṇḍala of the ground, the ultimate natural state of all phenomena, which is primordially of an enlightened nature within great purity and equality. Moreover, the tantra also shows the path, the various means that allow one to actualize this ground either directly or indirectly. Finally, the tantra reveals the maṇḍala of the fruition—perfect, total purity. In short, the tantra teaches the profound realization of mantra, as subsumed within ground, path, and fruition.
Where can I find more information on this deeper meaning of mandala. What is the mandala of the ground?