Several factors can cause these granola bars to not hold their shape. First, make sure you are chilling them thoroughly before slicing. Second, these are best stored chilled in the fridge. If left at room temperature (or in a hot car) they will soften considerably. Last, no-stir peanut butter works best in this recipe since natural peanut butter tends to have more liquid and add extra moisture. If you prefer to use natural peanut butter, try increasing the amount of oats, a few tablespoons at a time, until the desired consistency is reached.