What are the best storage conditions for cellared beer to ensure optimal aging and flavor development?

The best storage conditions for cellared beer to ensure optimal aging and flavor development are a cool, dark, and stable environment with a consistent temperature between 50-55F (10-13C). It is important to store the beer upright to minimize oxidation and keep it away from light to prevent skunking. Additionally, maintaining a humidity level of around 50-70 can help preserve the beer's quality over time.