Here I have a piece of sandpaper taped to a board in my studio. It is actual sandpaper which comes in large sheets. You can see the charcoal drawing on the paper, and the first application of color with pastels.
The drawing is from a photo I took while on a paint-out. I painted another scene from the park that day, and took a photo of this scene for later use in the studio. While painting outside, I use smaller sheets of paper, usually no bigger than 9x12 inches. I wanted to use a larger paper for this painting, 14x18 inches.