Fill the 4-inch growing container to the top with coarse sand. Spray the sand generously with water to saturate it evenly.
Clip a stem from the herb plant, removing it just below a leaf node -- the point where leaves attach to the stem -- to produce a stem between 4 and 6 inches long. Clip off any lower leaves from the stem to leave two or three leaves at the top only. Dip the bottom two inches of the stem in rooting compound.
Insert the prepared stem into the center of the sand in the growing container, pushing it down into the sand about 3 inches. Firm the sand around the stem with your fingers so the cutting stands upright.
Place the plastic food bag over the top of the container and secure it to the rim of the container with the rubber band.
Place the container in a location with indirect sunlight and temperatures around 70 degrees Fahrenheit.
Remove the bag every day and spray the sand with water to keep it moist. Replace the bag and the rubber band.
Leave the rubber band off to ventilate the herb cutting after you begin seeing new growth on the stem. Continue spraying the sand daily for another week.
Remove the bag completely and continue spraying the sand daily to keep it moist. Allow the stem to continue growing in the sand for another one to two weeks to give it time to establish roots.
Transplant the new herb to a permanent growing location -- a container filled with potting soil or a spot in an outdoor herb garden. Loosen the plant gently from the sand without disturbing the new roots and transfer it to a prepared growing location. Water the herb thoroughly immediately after transplanting it.