The odd thing is, they don't all really say the same thing. Most of them say come up with a concept so that must be good advice ... except that it really seems almost the same as come up with a character. So, I'll help you out a little bit by talking about some actual methods by which characters are created.
The number of stars on the flag is fixed at 12, and is not related to the number of member states of the EU (although the EU did have 12 member states from 1986 to 1994). This is because it originally was the flag of the Council of Europe.
Each star on the flag represents a state of the United States. The first stars were 13 states and the US flag had 13 stars; now the US has 50 states and 50 stars. The stars & stripes style of the US flag has its artistic merits too. The sophisticated blend of red, white and blue make it an attractive flag and the flag can grow more stars if the US should add another state.