The first method is to take a small glass with sloping sides, and a stack of Post-its, then split the stack of Post-its in half and put the iphone in the glass between them, like this:
If you want to turn the iPhone sideways to take a landscape-orientation picture or video, that works too, but it is a little trickier to get the Post-its arranged just right:
You want the sticky part of the post it pressed against the back of the iPhone.
Take the iPhone out of the case, then stand the iPhone up in the part of the case where the screen normally is, like this:
The third method is to get one of those cardboard insulating sleeves from Starbucks that makes it more comfortable to hold the hot coffee cup. This works best when the sleeve is brand new and the cardboard is still stiff. Stand the iPhone up in the coffee sleeve and take a timer photo:
Finally, if you have the Belkin flip case and the coffee sleeve, you can stand the flip case in the sleeve, turn the iPhone sideways, and put it into the top of the case like this: