We are likely enclosed within borders ---- like as if we were in the bass of a bowl. The reason being is because we experience air pressure.
This is more plausible than an infinite plane idea, but the fact that there have been NO observations of the border, edge, ice wall, or whatever one would seek to call it, nor is there even any solid agreement as to what sort of border there is- casts a massive shadow of doubt over even the more plausible FE theories.