Prepare a growing flat with potting soil.
Snip off a leaf of the Vietnamese coriander near the main stem with pruning snips.
Make holes in the potting soil for the leaf stems. Use the end of a pencil.
Slip the stems in the holes and press soil up around stems. Or, if you prefer, you can place the cuttings in a glass of water and put it in a window.
Water the soil to dampen it. Keep it mildly damp for 10 days to up to two weeks. After time is up, gently pull up on the leaves to feel for resistance. If the leaves won't readily come out of the soil, roots are forming. Continue to tend to them for at least two more weeks before transplanting into pots. If you root in water, roots will develop more quickly, and you should see the start of them in a few days.