Receptacle island in freestanding wall
If it's not part of the house then electrical codes for buildings don't apply to it.
That said you should meet or exceed the safety that electrical codes aim to provide.
It sounds like you are going to use a suicide cord to power it? DON'T! There is a reason they are called that.
Instead use an (singular) inlet or wire an power cord with plug into the structure, and make sure it's not a tripping hazard.