Frost builds up on the inner surfaces of your freezer because moisture from your fresh food attaches to the appliance's coils. This process is sped up if your door isn't sealed tight, or your appliance's self-defrosting technology is unreliable and needs repairs. The result will be frost and ice chunks that grow in size, until they've been chipped or drained away, and less storage space for your food. To prevent a lot of frost from building up in your freezer, be sure to never leave the door open for long periods of time, and close it tightly when you're done. In addition, occasionally check the temperature of your freezer to ensure it's consistent and stable.