First and foremost, make sure to mix your boxed cake mix; remember that you have to mix it according to the box's instructions. Next, ensure to divide your cake batter into your eighth-inched or nine-inched cake pans. Then, be sure to bake as indicated in the boxed cake mix's instructions.

After that, you must allow your cakes to cool completely. Next, ensure to stack the cooled cakes on top of each other on either your cake plate or cake stand. Then, you may cut out a shallow piece from one-fourth of the cake utilizing a knife; keep in mind that its purpose is for the monster truck going up a hill.

Next, you may blend your vanilla icing with some green food coloring; remember, begin with tiny drops of food coloring. And with this, do not forget to combine them properly. In addition to that, you can add more to achieve a tint of green that you desire. Besides, please note that it is always best to add bit by bit. The reason is that, at all costs, you want to avoid an extremely dark shade.

Afterward, make sure to take the green food coloring. Then, make sure to ice the whole cake. However, keep in mind that you may leave out the spot you cut out. With this, you can utilize a butter knife. Likewise, it is okay to use a baking spatula to ice your cake.

Then, be sure to frost the spot you cut out using your chocolate frosting. As another option, feel free to use the chocolate icing to ice a bottom border; keep in mind that you need to do this around the cake. As a result, it will undoubtedly provide a scenario of the muddy road the monster truck climbed.

Take your Oreo cookies. After that, make sure to remove the white icing from the center. Also, be sure to crush the cookies utilizing a potato masher in a bowl. Likewise, it would be okay to put them in a large Ziploc bag. Afterward, you may smash them with your rolling pin.

Afterward, ensure to sprinkle your crushed Oreo pieces on the chocolate frosting in any way you desire. Then, you can put chocolate malt balls; bear in mind that this will imitate giant rock boulders in your chocolate icing. Finally, you may add the monster truck. Likewise, you may put birthday numbers, including finish line flags.