Take the sky and upend it onto the earth
How do we generally look at a landscape? The land rolls out in front of us and the sky lifts up from the horizon way off in the distance.
A simple painting of that could be: the bottom half of the canvas would be green and the top half of the canvas would be blue.
Consider this on a painting: the land is fully, from the bottom to the top, covering the canvas. It’s a gorgeous green field fully covering the canvas. The painting is a green square.
And on the same painting, consider that the sky is fully, bottom to top, covering the canvas. It’s a gorgeous, ultimarine blue sky that is covering the green field.
What you have now is a blue square covering a green square.
Saying it creatively, I’ve literally placed the sky over the land and I’ve opened the sky up here and there so that the land can peek through. In this painting, the sky and the land are one.