Sheet vinyl doesn't go all the way to the wall behind the fridge. How to install a new floor?

There's about a foot of what I think is plywood showing at the edge of the vinyl in the entire space the fridge occupies. I think at one time they had a larger fridge and it filled the space such that no one could see the lack of flooring. But how do I even this out to put down a new floor? It's not that the floor itself isn't level, there's one less layer back there. Wouldn't putting ANY type of NEW flooring down without fixing this lead to the whole thing being out of level?