you can float java fern too...Just drop it in the tank, although if you want it to be more of a stable part of your scape, tie it to rock or wood and it will eventually ahdere to it. The roots get nourishment from the water column, so it doesn't matter~
Yeah, you can float ferns pretty easily, it's just a matter of how heavy the root clump is. If I had a camera I'd take a pick of my RCS tank, which has probably two-dozen inchling ferns floating in it right now. You don't need to tie them down or anything, as all that matters for the plant is that the roots are submerged and not buried.