From the bottom

We always use one piece of stone on the spillway.

Also, we always run the stone veneer down below the waterline and have the tile meet from sides. Never meet at the top of the tile.

That "finger ledge" will a be a point where the water from the spillway above, will hit it's top and splash around. Even if the spill stone's lip extends beyond it.

We apply a water proofing material prior to the tile application and most certainly when natural stone is used as a veneer.

@Mystic where can I learn more about the need for water proofing material? Is there some concern about water splashing onto that stone veneer? Also, is there something you would do with those gaps between the veneer and the finger ledge?

Prior to to tile and or stone application, we apply Basecrete waterproofing. We use this to waterproof interior pool and spa shells and if we have access to the exteriors, we will apply it there as well.

My preference is to wait the 28 days until the gunite is fully cured before application. Others may differ.

The surface is acid washed and then power washed prior to application.

The stone you have set is usually back buttered with mortar to give the appearance of a dry stacked stone which is fine.

The interface with the finger ledge and the water coming from above, may find it's way along that ledge and leak passed the coping stone on either side of the raised spa.

There are some clear, flexible, waterproof caulks available that could be used to seal the top of the finger ledge. I would first see how the water travels once your pool is complete. You can easily shut down the spillway for 24 hours to apply the caulk.

There is no topical waterproofing or sealers that work for pool applications. It all starts at the beginning phase at the structure's surface.