One of my friends at Pixel-Mesh took a few household tools and the leftover pizza box from his lunch and fashioned it into a homemade flash snoot that yielded surprisingly good results. A snoot restricts the light and allows you to direct it at a specific location, helping you to eliminate “light spill”
A razor knife, builders square and a roll of dark colored duct tape (you knew duct tape was going to make an appearance somewhere).
Using The Top of The Box
Cut the outline of the snoot shape and cover the cardboard with a layer of duct tape.
Fold Into the Proper Shape
Fold into the proper shape and tape it into position.
Attach to The Flash
If you sized it right it will fit on the flash without taping it.
With the flash attached to a Canon 5D MKII the results are not bad, not bad at all.