We used 8-10.5 sheets of paper.
and then fold the right upper corner down into this fold.
Angling about half-way up the triangle, start at the bottom and cut all the way across with scissors.
If you’d like two stars together, for hanging over a doorway or something, I’ve found the best way (though not perfect) is to just place tape inside the stars, making sure to get the two halves as flush as possible. I tried cutting tabs, and different ways, but tape works the best that I’ve found so far.
It’s not perfect, as I said, but they’re still really pretty, and not really noticeable.
To ensure a good fit, fold two papers,
I put the tape on the inside after they were decorated, and then hole-punched them and hung them with ribbon.