You’ll want to use a 9”x 13″ pan so that the texture and consistency are right. I’ve used an 11″ x 7″ pan before, and it turned out a little too thick, which changed the delicious texture of the dump cake.
Because dump cakes are so gooey and moist, it can be hard to determine if they’re done. It’s normal to see some wet spots and some spots that are more crisp and done.