A lot of people don't know this, but there's actually no laws or rules about how you have to arrange stars on the flag, other than that they have to be white on a blue field. You can have a flag with one big star in the middle and 49 tiny stars around it, and it is valid as the US flag, you can have a mess of them, they can be upside down or sideways. I don't just mean the government can decide, I mean that you can make a flag like this and fly it and it is the US flag.
Convention dictates though that all stars be of the same size, symbolism for the states all being equally co-sovereign over the union, and the arrangement revealed after a new state joins the union is usually what gets manufactured and becomes the not so official "official" flag.