For your final submission, you will need a website to document all your work. This is probably the single most important part of your project; who cares if you make something cool if you aren’t able to communicate that cool thing to us? There are plenty of free site builders out there if you don’t want to put the website together yourself from scratch. I haven’t used all of these, but most of these are free or have a free option, and many have some sort of privacy controls. That way you can protect the site during construction (though you will need to publicly post your submission at the final deadline)
* These should have privacy control settings.
For inspiration on successful websites for similar contests, I would suggest you look at winning entries from a contest called biomod.