The simple answer may be - you can't. Partly for the reason below and partly because leaves usually fall off because they are dead or unhealthy.
The only way I know to grow rubber plants from cuttings is to leave the leaf attached to the plant. Cut a heel away below the stem joint leaving more than half the leaf stem attached. Put the heel into moist compost/moss wrapped in polythene or similar and wait for roots to form. When a substantial root growth has been established detach from the stem. However I have had a very low success rate (about 40%) even with this method so unless you have a rubber tree that is old and discardable it may take several leaves. Adding hormone rooting gel may help.
I don't know whether this works but I would be inclined to chop it into several sections each with a leaf connection node at the base. Dip each in hormone rooting gel and keep the compost moist and warm throughout. Then trust to luck. You are hoping there is enough starch left in the stem to create a leaf up to the point where photosynthesis takes over. For this reason try a range of stem sizes. The newer stem should be best for rooting. Good luck.