The best early base location is the one that makes daily production simpler. Space, movement and useful nearby resources usually matter more than scenery.
Prioritize usable flat space
Workers and structures are easier to manage when the base is not fighting the terrain.
Watch worker pathing
A location can look good but perform poorly if workers constantly struggle to reach jobs or storage.
Value nearby resources that remove chores
A convenient resource is useful when it reduces gathering you would otherwise repeat manually.
Leave room for the next systems
Avoid locations that become cramped after only a few production additions.