Here is the pond dry-stacked and on a test run. I let my mortar set over-night before I put any real weight on it as the water feature turned out heavy.
I cut a drip edge underneath the block that the water runs off of, and all the blocks are tilted slightly forward to help any water turning backwards, to eventually fall forward.
After the test run, I pulled all the blocks to check, and sure enough all the water seemed to be moving forward.
After that, I set all the flag with block adhesive.