Preheat your oven to 350°F (175°C).

Prepare the au jus by combining beef broth, Worcestershire sauce, garlic powder, onion powder, salt, and pepper in a small saucepan over medium heat.

While the au jus simmers, slice the French bread lengthwise and place it on a baking sheet, cut sides up.

Layer the sliced roast beef evenly over the bread, followed by slices of provolone cheese.

Drizzle a spoonful of the prepared au jus over the beef and cheese layers.

Close the sandwich by placing the other half of the bread on top and pressing down gently.

Bake in the preheated oven for about 15-20 minutes, or until the cheese is melted and the bread is golden and toasty.

Remove from the oven and let cool slightly before slicing into squares.

Serve the French Dip Squares warm with the remaining au jus for dipping.