Here is the plain jane, waiting to be decorated.
I simply sewed a single stitch through the center of the strips (don't backstitch).
I tied one end of the strings in a knot. Then with the opposite end, I held ONE of the threads and pulled the fabric down into a ruffle.
I just laid them across the purse as I went to judge how much to "ruffle".
I didn't have any black fabric so I found an old oversized tank top that I don't like any more to cut up.
I used a hot glue gun to glue the ruffles on the front. Three rows of ruffles did it for this size purse. I like that the top is still tan. I laid another ruffle on the top, but didn't like it as much. Repeat to make the back match the front.