I love these kind of projects for children--there is no "right way" or "wrong way", you can use anything you have on hand, and they get to understand that art comes in all shapes and sizes!
Madeleine wanted a blue background for her garden, so she took a piece of regular chalk and rubbed the paper.
and, since we were gluing things to the paper, I gave her a paper towel. She rubbed the excess off the paper so the glue would stick. She washed the chalk off her hands, and then set to work! She took an oil pastel, drew on grass, then applied glue to make a flower.
A tulip, a bird with pastels (and a beak of felt), buttons for flowers...so fun! I love how happy Madeleine was with her collage, and knew just when it was complete!