Flat rate boxes are a great way to save on shipping and makes it easy to set your shipping settings on your website. I mostly ship small stuff so I go through a lot of small flat rate boxes. They are a pain to load and very hard to pack a lot of stuff in. I decided to make a tool that will help with the process. It holds the box open like a normal box so you can cram it full off product and then seal it.
I have uploaded it to Thingiverse so others can make their own.
Here are some pics of the box in action.