Pattern Illiterate (Beach/Market Bag)

Hi all!  I crochet by sight, (Youtube).  I don't know how to read or write a pattern.  I've only been crocheting for less than 3 years.  I can read some diagrams.  Anyway, here is my dilemma:  I have invented my own crocheted beach/market bag that people are going wild over.  I want to share how I made it, but I don't write patterns.  I can tell you that the bag is made of 13 granny squares that are 7"

wide, medium weight cotton, no. 5 crochet hook.  Here is a photo of it.  If anyone can figure out how to write a pattern, or just play it by sight, be my guest.  Anyway, here is a photo.