Developing efficient and durable oxygen evolution reaction (OER) electrodes for alkaline water electrolysis requires not only catalytically active components but also strong interfacial integration between the catalyst layer and the conductive substrate. Herein, we report a one-step hydrothermal route for constructing a six-metal NiZnCuCoMnFe LDH-based heterostructure directly on copper foam, denoted as M6-LDH/CF. Rather than forming an ideal homogeneous multimetal LDH phase, the synthesis produces an integrated architecture consisting of a six-metal LDH nanosheet framework, segregated Co/Mn-containing oxide or oxyhydroxide surface phases, and a reconstructed Cu/Cu2O/CuO interfacial region derived from the substrate. Structural analyses indicate that differences in hydrolysis, oxidation, and precipitation behavior among the metal species, together with substrate oxidation under hydrothermal conditions, govern this non-ideal growth pathway. The optimized M6-LDH/CF electrode exhibits overpotentials of 181, 392, and 502 mV at 10, 50, and 100 mA cm−2, respectively, and maintains stable operation at 50 mA cm−2 for 100 h. Post-OER XPS further reveals pronounced surface-state evolution, including Cu oxidation, Zn leaching, and the formation of more metal–oxygen–metal coordination environments, indicating that M6-LDH/CF functions as a precatalyst architecture that evolves toward a more oxidized working state during operation. These results suggest that controlled non-ideal in situ growth can be used constructively to fabricate integrated multimetal OER electrodes with favorable activity and operational stability in alkaline media.