This honestly isn't very interesting. It's just a box, and the story is about how it's contained, but no one is going to care about how the Foundation contains a box. For me, containment procedures as the driving point behind an article only work if they are either ethically questionable (231), clearly use up tons of resources because of the sheer danger the object poses, or the interesting methods used to contain a difficult object.
Why is the box there? Box shaped objects probably don't occur naturally very often, so maybe someone created it. If so, why? These might be questions worth pondering.
A word of advice I have for you is to take your time. Just because you joined a writing website doesn't mean you have to write something right away. I joined this site in December 2018, and I didn't post an idea in this board until July 2019 or so. There is nothing wrong with spending a few months acquainting yourself with the site. To me, it feels like you're forcing an idea because you feel like you have to have one, it doesn't seem like you're very interested in this one. Don't force yourself to write for the sake of it. Take the time needed to develop an idea before presenting it here, and you'll be much more likely to have a good idea later.
Read articles, read comments, read this forum, join the IRC chat. As you lurk the website you'll become more familiar with it, and what readers want to see. Some people get it instantly, and others don't, but that's OK. You clearly have a lot of passion for this, but you don't have to jump in right away as soon as you're 15.
My advice is to stop posting ideas here until you are invested in the concept itself, and not the idea of writing any SCP.
