These flowers are made using chigiri-e technique, adapted for children.
We use plain white toilet paper, although it's considered unsuitable for chigiri-e. Place pieces of paper on a plastic bag so that they don't touch each other, and colour them with water colours. Don't draw the paintbrush, just touch the paper allowing it to absorb the paint. Let dry. Tear pieces of desired size and shape from the paper and glue them on a sheet of paper according to your design.
I must say that even the most restless of my kids likes sitting tearing and gluing pieces of paper. Here, for instance, one of the children's "creations":