So I need to learn how to make a simple flag for the sides of an 16:9 picture that only has 4:3 footage or images in it like they use on ESPN or other networks to make up for the lack of image on the sides.
Zaxwerks 3D Flag,
Wave Warp, left edge pinned, crank up the Wave Width, Direction 45 (animate this) wiggle or time*
You might need Grow Bounds above the Wave Warp to stop any clipping
animating fractal noise and using it as a displacement map,CC Page Turn, mesh warp and freeform. wiggle or time http://library.creativecow.net/articles/lindeboom_kathlyn/flag_freeform.php
If you don't mean "flag" as in the cloth thing that flutters in the breeze, your options are almost unlimited. You'd probably want to start by having a design of what you want.
I'd work in 1920x1080. If you have to go to 720, you can always nest it inside a 1280x720 comp. For compositional purposes, keep a 1440x1080, square-pixel solid handy. if you place it at the center of the comp, it will help you see the areas on the sides of the comp that will be your primary focus.
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA