Super cute bag!
if I am thinking of same tutorial, it was an interfacing that they laid out flat and sewed strips of fabric on top? Gemini showed how it crinkles up yet still retains shape.? I also tried to order and they were out but I found some at Joanns. It was such a challenge for me to sew with! Hard to maneuver, a little slick. I used it with a different pattern. "the Friday Bag". Loved the concept and the completed bag but It might not have been the best use of the interfacing.