To make the Au Jus- in a saucepan combine water, beef base, celery, onion, thyme, salt, and pepper. Simmer until vegetables are tender. Strain and places into small bowls for serving.
Pre-heat the oven to 350 degrees. Split the slider rolls in half. Lay the bottom half of a slider roll on a baking sheet. Top with a folded slice of roast beef, top with Swiss cheese. Place the top half of the slider roll on top of the cheese. Repeat until all of the rolls are used up. Place into the oven and bake until cheese has melted. Serve with Au Jus.