I would just set on top of a gritty mix and keep in a shady spot. Could you take a pic of the plant in question so I can see the roots:)?

And prop it up with rocks if it keeps flopping over on you.

@Kara here is a photo of the roots. I took it out of soil and am leaving on top of gritty mix in the shade.

@Kara, so basically you think the entire root section is rotted and will die?

They root quickly. You can put it in perlite, gravel, or pumice, and just leave it alone. No need to water until the roots come in.

after you cut it down like Kara suggested. You are probably going to lose the lower leaf when you cut the rotted part off. It's fine, just cut it back until you see healthy stem, toss the lover leaf, leave it out for a few days to callus over, and stick it a dry medium. It will put out new roots very quickly.