This bag took so long, because apparently you will need a million layers of white paint on top of red fabric to stop it looking pink. But then you will iron it, in order to set it and it will turn pink again and you will have to repeat this so many times to get it to stay white (-ish).
But other than that, it's pretty straight forward, stencil the design onto a sqaure of fabric using acrylic paint. Iron it to set the paint. Stitch the design into a bag, and add straps.