This build is quite easy. This is my first post here so leave me feedback.
You need 9 wool (any colour depending on your flag.)
You need 5 fence posts or more if you want it higher.
Place half of your fence posts in a straight line heading up.
Then place the other half sticking out of the 2 top fence posts.
Place 3 of your wool onto the top fence posts.
Do the same but move it one block backwards and connect it to the other wool.
Do the same again.
You have a waving flag of your country (or maybe something else)!
-uK RAPiiDz
P.S Check out my channel at http://m.youtube.com/user/uKRAPiiDzx?feature=guide