Add soilless potting mix to a flat to within 1/4 inch of the rim. Water it until excess flows out of the drainage holes.
Take a 3- to 6-inch-long tip cutting off the ivy with scissors. The tip has the plant's youngest growth. Verify that the section you choose has three or more leaf nodes before cutting it.
Remove the leaves from the two nodes nearest the cut end.
Plant the stem's cut tip in the moist soilless mix. Firm the growing medium around the base of the cutting to keep it in place.
Water the cutting at planting, applying water to the soil and misting the foliage.
Slip the flat into a clear plastic bag. Insert stakes in the soil to keep the bag from collapsing on the cutting if necessary. Close it to hold moisture and heat inside. Place the flat in the shade.
Leave the flat in the bag for two weeks. Irrigate the cutting regularly to prevent the soil from drying. Open the bag to allow excess moisture to evaporate if condensation covers the inner walls of the plastic bag. Reseal the bag.
Move the soil carefully away from the stem's base two weeks later. Continue to check the stem daily until you see the first roots. Open the bag when that occurs. One week later, remove the flat from the bag. Allow the rooted cutting to develop seven more days before transplanting it to a permanent location in a pot or outdoors.