How was God created?
The question assumes that God is a creature. God is categorically different from Creation, since His Essence (What He is) is Being Itself.
We can know this from the following argument.
1) Assume that every thing owes its existence, or being, to a previous being.
2) This chain cannot regress forever, since that would require the completion of an infinite series. A completed infinite series cannot exist in actuality; it would not be infinite or unending.
3) There must then exist a Being which does not owe Its existence to any other being.
4) We call this Being, God.