Bourbon whiskeys are known for their complex layers of flavor, which come from the mash (grains) used, the amount of time the bourbon is aged, and the type of oak barrel it's aged in. Distillers may use a few methods to flavor the bourbon barrels themselves, which further influences the character of the bourbon.

Charring is the most common method of preparing a bourbon barrel, and involves setting the barrel on fire and allowing it to burn for around 30 minutes. Different distilleries want different flavors, so shorter or longer charring may be done, and after burning, the barrel is cooled, the bourbon is added, and the barrel is sealed.

Another method is called toasting, in which the barrel is heated slowly at a lower temperature instead of extreme heat. The low and slow method causes the heat to penetrate deeper into the wood, exposing more layers and allowing the bourbon to pick up flavors that might be missing from more conventional charred bourbon.