Golems are commonly made of earth or sand and on rare occasions even metal. Like other earthen constructs, golems come into being by fusing materials around a core; a soulstone. This functions much like the brain or the heart, and is commonly tucked away in their heads. (This is the weak point everyone will be aiming at when trying to bring it down.)
Although they can be found in nature, especially near ruptured mana veins, they are mostly artificial.
Because they are relatively simple to create (and on top of that can be much larger and stronger than a common foot soldier) they have become a staple of not only garrisons but also daily life in the cities of the Sands. Their configuration and use vary greatly; it all depends on the time and effort their creator invested in them.
Note: Construct (artificial creature imbued with mana); most commonly crafted by the arcane artisans (summoners) of the Sand Kingdoms