This is for those building with the DPR House Builder in Unity and struggling with the flashing building issue with Dynamic Skies ON. I promise that the Blender part should be less than 1 minute once you know what to do. You really do not need to understand anything in Blender other than what is shown in the video. The end of the video also shows how to make a prefab of your custom object and import it into another project if you desire.
The problem is from overlapping vertices in Unity. The reflective water patch eliminates this Unity issue. Newer versions of Unity eliminated this issue. Where we are with PG1, it will require you to remove the overlapping vertices. This is why even the bulkheads PP makes for Florida Glades flash. They are just pieces that overlap and the Dynamic lighting doesn't play nice with it.
But, better made objects with no overlapping vertices do not have this issue. It's why I moved all my building to Blender. I honestly like building in Unity better because of visualization and speed. This could be the happy middle ground. Build in Unity. Export to Blender for a quick join and remove of doubles. Back into Unity and add Materials.