Do you think this would make a good wall around my above ground pool. If for example I started with a ground layer, it dry's then the next layer?

No, I don't think so as each part of the mold is separate from the others. You will have piles of odd shaped pieces rather a continuous wall. Assuming you could actually stack the pieces to any height they would be structurally unsafe unless you mortared them together. There are easier and better options than this.

For horizontal forming only.