This was surprisingly a very easy project. Brad went and got us some plywood from Home Depot and after lots of measuring, cut the board to size. We also had to cut a small piece out of the back where the hoses are so that the counter would be flush with the wall. Before we moved on, we made sure it would fit perfectly.
I decided to stain the board instead of painting it. Over the next couple of days, I did one coat of dark stain and followed it up with a couple coats of polyurethane to protect it.
While I worked on that, Brad installed the support boards into the walls to rest the counter on top of. We put these about an inch above the washer & dryer. You DO NOT want to put the counter directly on the washer & dryer because it will rattle! Note: If your counter space is going to be long, then I would suggest having support in the middle or adding legs to your counter (see pic above).
All done! I am loving my new folding space.