To start, preheat your oven to 350 F.
Apply cooking spray to three round cake pans.
Lightly sprinkle flour on the pans, and keep them aside.
Add the flour, Hershey's cocoa, sugar, baking powder, baking soda, and salt to either a large mixing bowl or a Kitchenaid stand mixer.
Make sure to completely blend the milk, oil, eggs, and vanilla extract together. In the end, pour the boiling water into the mixture and stir thoroughly until all the ingredients are fully incorporated. The batter will have a very runny consistency.
Distribute the batter evenly into the cake pans that have been either sprayed or floured.
To ensure the cakes are fully baked, it is recommended to leave them in the oven for approximately 30-35 minutes, or until a toothpick inserted into the center of each cake layer comes out clean. When you are all done baking the cake, allow it to cool for at least 10-15 minutes before removing it from the pans.
After taking the cakes out of the pans, relocate them to a wire rack to cool thoroughly.
For achieving uniformly even layers, my suggestion would be to make use of a cake leveler or a serrated knife.
As the cake layers are cooling down, you can begin preparing the frostings.