The formula is: Two squares at a measurement for the background and one square 3/8" bigger for the geese (This will yield four migrating/staggered geese)
For the border, I needed a finished six inch border, which dictated that my background squares would be five inches, and my goose fabric would be a 5 and 3/8"
With this formula, you can pretty much figure out how big to cut your squares for the width you need.
Here is a picture of the border I created for IRR2 and what I will be teaching you to create.