That Is simple.
They should just twist the time and gravity, similar to how black hole works, so when in chapter 2 - Shadow of the past,
Gandalf is talking to
Frodo how he should toss
the ring into the Mount Doom, he should just raise hand, and let the ring.
Ring would be pulled upwards by gravity of Mount Doom that is standing upside down, and already torn the roof of
hobbit house.. pardon.. hill...
Eventually, it would suck up the Frodo and Gandalf.
But, what is 2 lifes if that would save the
middle earth?
(
Sam might be saved by thorned branches of the
plants that would hold him).
All above is very possible... unless...
Sauron himself twisted the whole time gravity aspect, and was upon inverted Mount Doom, and just grabbed the ring, when Frodo let it.