I made a mistake and lost an Amorphophallus decus-silvae seedling to root rot. I cut the leaflets off the petiole with a scalpel, dipped them in rooting hormone, and placed the cut ends in loose sphagnum. After three weeks under a humidity dome at 26C, all three have formed callus tissue and two have visible roots. They've been transferred to containers of very well draining soil topped with a layer of sphagnum, providing the same conditions except for the soil being ready to receive the roots.