Unfortunately, he presented his work in the form of Euclidian-style geometrical proofs, complete with definitions, axioms, corollaries, etc. The end result wasn't very accessible, and has been largely neglected or derided since (although Albert Einstein endorsed it, among others).
Anyway, here's my attempt to adapt that aspect of Spinoza's work to the form of a Biblical parable, so Creationists can follow along (needless to say, it's a vast oversimplification of Spinoza's thinking):
In the beginning was God.
And God spoke, saying, "Now I shall make a world." And He considered all the possible worlds He might create, so that He might choose the best among them.
With His infinite intellect, He was able to behold in His mind each possible world as if it were already made. He was able to see simultaneously every instant of each world, from the first moment of its birth to the last moment of its destruction. He could see each potential creature within each world, and could experience every thought that creature would think, exactly as if it already lived and breathed. He could see every decision that creature would make -- and every possible choice meant another possible world, and He could see them all in their infinitude.
And of all these possible worlds, He chose the one He found most perfect; and He contemplated it in its entirety. He saw every particle of its being and every moment of its whole vast history laid out before him, exactly as He would make it -- down to the innermost thoughts of every man and woman and beast within it.
And He said: "Let it be."
And He beheld his new-made world again, and it was unchanged in His perception.
For to His timeless perfect sight there was no distinction between the potential and the actual; what was, and what was not, were one to Him. And so, to Him, "creation" had no meaning. Nor did He need to "design": to Him all possible designs were eternally equally real.
And God thought on this, and was pleased.