After baking, make sure you allow the bars to cool sufficiently before slicing them if you want them to stay somewhat neat and intact. For me, this means planning ahead and making this recipe before bed and allowing the bars to cool overnight in the pan. But if you can't wait overnight, or even for a few hours for them to cool, you can dig in knowing they will be super messy and could fall apart. But s'mores are messy after all.