Choose a container that is sturdy enough to hold the cutting upright and won't topple over under its weight. A vase is ideal, provided it has a wide footprint. You may also choose a transparent container so that you can better tell when the cutting roots. Disinfect the container by soaking it for 15 minutes in a solution of 1 part of household bleach and 5 parts of water. Rinse the container with clear water before filling it, halfway, with water for the cutting.
The rubber plant, when cut, oozes latex which some people find irritating to the skin. It may be fatal if ingested. Wear rubber gloves to protect your hands when working with the plant. Use pruning shears to snip a 6- to 10-inch piece of stem from the plant. Cut the stem just below a leaf node. The mother plant will leak latex as well, so protect furniture and flooring until the wound calluses over.
Any leaves on the bottom of the cutting will rot if left underwater, so remove them by cutting them off. Allow two small leaves or three large leaves to remain at the top of the cutting to help the rubber tree plant carry out photosynthesis until it produces roots. Place the cutting into the water and place the container in a shady area, out of direct sun.
Change the water in the container daily to help supply the cutting with the oxygen required for rooting. Rubber tree plant cuttings require lots of humidity and there are several ways of supplying this. A portable humidifier, placed next to the cutting will work. Or, create a humidity tray by filling a shallow pan or tray with pebbles and filling it with water. Place the container on top of the pebbles. Add more water to the tray as the water evaporates.