You're asking yourself what are these left pages.
So in my journal, the left pages are reserved and used for testing materials and making swatches of color. Sometimes these turn into my favorite pages after I add some drawings and doodles. But the starting of these pages are just me "playing and messing about" on the opposite page of my journal. I'll give you a few examples below of what some of my "left pages".
The scribbles and swatches and blocks of color that are already there help give me a jumpstart. I add some pattern work, some doodles and drawings and I create something magical from what started out as just messin' around. I think the playing around part is where you'll find that magic