This is how the Vanthric Haimarchy grows its garden worlds.
The surface of the planet is covered in dense layerings of foundational Jhoutaioan Coral Spores, which begine eroding at the rock and converting it to softer materials for hard coral to settle in and grow upwards from.
As these modified corals grow, they grow in patterns of fractal logic, forming massive geometries and hive-like structures. Soft coral is seeded onto these structures, growing into forests which are then populated with carefully chosen, modified, and cultivated life. Not a single species within this ecosystem is unmodified.
As the ecosystem establishes, colonies of secondary demand—mostly trade and support—move in, habitating the now rich and stable structures of the coral. As settlement ongoes, these structures take on new shape, personalized by hand and subsequent generations of culture.