A good base location makes your normal survival loop easier. It does not need to be the prettiest place on the map; it should reduce repeated travel and leave room for the systems you actually want to build.
Prioritize easy access
Choose a location you can recognize and return to without complicated navigation.
Think about recurring resource trips
Nearby wood, food, caves or useful terrain can reduce the chores you repeat most often.
Choose terrain that matches your building style
Flat land is convenient, but natural terrain can be useful if you prefer smaller or embedded builds.
Leave enough room for the next stage
You do not need a final megabase immediately, but avoid a location that becomes frustrating after a few additions.