The expression "more or less" means "almost" or "basically".
When you say that something is "more or less done", it means that it's basically finished. It might need a little more work to be perfectly finished, but it's finished enough.
Some other examples of this expression are:
more or less the same
more or less equal
more or less finished
You can also use "more or less" at the end of a sentence. For example, after explaining how to do a job to a new employee, you can say:
That's it, more or less.