What looks "simplistic", isn't.
At first glance it may look like a coat of paint, cut and paste, and there you are.
For starters, that doesn't take in the idea, choosing the elements/images, composition (where to position everything), colour choices, and pulling it all together.
This 12 x 12-inch painting started out with a lot of colour. Smooshing bright colours over a canvas is lovely, but I wanted to use a photograph, and it didn't work, so I added pieces of paper here and there and painted many layers over it, in white, light taupe, cream, a little grey.
The colour would come from the butterflies.
I began with two, and played around with a few more until I was satisfied with the composition. I chose the Monarch butterfly, with blue ones to make it pop.
Simplicity is the removal of the useless and the unnecessary--source unknown