I like having containers to hold small electronics parts or headphones or other objects to keep them from running around inside my briefcase. I've been using a more rectangular case I made for months now. The thing with that one is that it has sharp corners and I often end up poking and scraping my hands. That won't happen with this design.
Print the two files. You shouldn't have much cutting to do but because of the handle on the lid, you will probably have to trim excess strings. It should work well with friction alone.