Step 1: Preheat your oven to 350°F (175°C). Lightly grease a 9×13-inch baking dish or line it with parchment paper, leaving an overhang on the sides for easy removal.
Step 2: In a large mixing bowl, combine the boxed cake mix, eggs, and vegetable oil. Stir until everything is fully mixed; the dough will be thick and sticky.
Step 3: Fold in the chocolate chips and any optional add-ins like chopped nuts, festive sprinkles, or candy-coated chocolates, ensuring they are evenly distributed.
Step 4: Scoop the dough into your prepared baking dish. Use a spatula or clean hands to press it evenly into the pan, making sure the corners are filled and the surface is smooth.
Step 5: Place the pan in the oven and bake for 20 to 25 minutes, or until the edges are golden brown and the center is just set.
Step 6: Once the bars are done, remove the pan from the oven and let it cool completely on a wire rack before slicing for clean, even cuts.