Here you go, this is how I did a flag (for fun)
Ist find the flag
Then glue a bit of tin foil on the back, making sure that there´s an edge of paper free to allow complete glue-ing, otherwise the tin foil tends not to stick properly, or slides when putting the two sides together. Best glue I´ve found is normal wood glue.
Lay the flagpole on the paper, here a metal pin and fold carefully together. Here it´s good to rub the two sides flat using a clean cloth (or similar) because the glue tends to collect dirt from your fingertips, no matter clean your hands are.
Let dry, doesn´t take long and the flag can now be shaped as desired!