Put your milk crate on top of your foam and trace around it with your pen. Cut the foam with a utility knife along the outline.
Set your milk crate upside down, so that the bottom side is facing up. Put your foam on top of the upended milk crate so that it functions as the cushion on your ottoman.
Drape your vinyl tablecloth over the foam and milk crate. Use a tablecloth that coordinates with the colors in your home or a neutral that goes with a variety of color schemes.
Fold the vinyl tablecloth over the milk crate like you are wrapping a present. Basic hospital corners will keep corners looking crisp. Secure each fold with a staple.
Fold raw edges under the base of the ottoman so that they are not visible. Staple in place and then cut away any excess material before use.