note: this question was first asked on Worldbuilding.SE, then on Politics.SE. The basic premises are the same, but you should go look at them, too.
Sovreign nations are, typically, plots of land where certain laws hold. To establish a new nation, one must wrest control of a plot of land from its previous owners (independence) and get other nations to recognize your sovereignty. If there is no current owner, then you can skip straight to step two.
It just so happens that I, being a free person, own my body. Can I establish my physical corpus as a sovereign nation?