The cast of characters: An iron, a water mister bottle, a rubber stamp, and velvet. The velvet must be made of rayon or rayon-acetate.

Set your iron on the wool or cotton setting with no steam.
Mist both sides of your velvet lightly, with water.
Place the velvet nap side down over your stamp. While I'm using a foam stamp here, a regular hard rubber stamp is preferable. The foam stamp starts to melt after a few uses.

Press the iron on the fabric over your rubber stamp. Do NOT move the iron, just press for 30-40 seconds. Use a piece of scrap velvet to start with so you can determine the time that works best for your fabric.

Lift your iron and look at your amazing handiwork.

Move the stamp to anew section of fabric and continue with your design.