Line a 9-inch square pan with parchment paper and set aside.
Put the oats in a large bowl.
In a small saucepan over medium-high heat, bring the maple syrup to a boil. Once it's bubbling, mix it in the oats, along with the peanut butter, any of the optional ingredients and your "add ins".
Quickly mix everything together as it will become very hard to mix if you wait.
Transfer the mixture to the lined loaf pan, and press down very hard to pack it tightly. This will help the bars stay together. If you want to add more toppings on top, go for it now! Put the pan in the fridge or freezer for 1 hour then using a serrated knife, cut into 16 bars.