I made an appointment at the Henna Cafe Marrakech, while in Morocco. The artist came to my Riad, and did all of the designs by hand!
First, she mixed the red henna powder with eucalyptus oil, and water (I think?), and some other natural oils. It makes a thick green paste which she put into a syringe, to pipe the mixture on like decorative frosting. The needle attachment actually made it easier for her to do a more intricate design. Note, there is no injecting here, just decorating on the skin, not IN it...
She started with my feet.
Then did my hands. I chose to do my palms, rather than the tops of my hands. I don't know why, I just wanted it that way.
The design came out looking like this.