Something I’ve done in sashing when at a loss is do a wavy line in one colour and then do a second wavy line that crosses back and forth in a second colour. It’s easy, can be done free hand (fmq) or with a walking foot and actually looks pretty good. The triangle zigzag pattern is an easy one to free motion quilt and doesn’t have to be perfect and quilts up quickly. Google Angela Walters, Quilting is my Therapy, she uses it all the time..