The best spot from which to inspect the installation of the valley flashing is:

The installation of valley flashing is critical for ensuring that water is properly diverted away from the roof valleys and into the gutters. Inspecting from the eaves provides the best perspective for evaluating the valley flashing's alignment, integrity, and condition. At this vantage point, the inspector can clearly observe how the flashing is integrated with both the roofing material and the surrounding components.

Inspecting from the roof itself may offer a close-up view, but it also entails safety risks and may limit the ability to see how well the flashing is performing in conjunction with other building elements. Looking from the ground provides a distant view that may not reveal details about the flashing’s installation quality or condition. Inspecting from the attic primarily focuses on the internal structure, making it difficult to assess the exterior installation and functionality of the valley flashing. Therefore, examining from the eaves strikes the right balance of safety and detail for this specific part of the roofing system.