But rather than the normal canvas you'd expect, he's working on a large, and very old, cactus plant.
And on these plants he depicts scenes of suffering by his Palestinian people with remarkable -- and haunting -- clarity.
He talks me through the five works he's already completed. "In the first, there is an old woman screaming; she screams against the situation on the ground," he tells me, referring to the decades-long struggle between Palestinians and Israel.
"In the second her hand holds a key, which is the symbol of the right of return for the Palestinian people," he adds, a reference to Palestinian demands to go back to the houses and lands they left in the war that accompanied the foundation of the state of Israel in 1948.
"In her other hand, in the third picture, she holds the cactus fruit, a reminder of the patience she needs to resist the situation around her. The final two pictures show children, symbols of the future. One shows a baby being clasped by a pair of old hands -- representing the continuity of resistance throughout life."
The final creation is perhaps the most profound -- it shows a baby being breastfed from the cactus plant, through a hole made by a bullet.
Ahmad's choice of canvas is full of meaning. In Arabic, the word for cactus -- saber -- is the same as the word for patience. For Palestinians, the plant has always been a symbol of patience, particularly so in the wake of what they call the Nakba, or "catastrophe" in 1948.
Very carefully, he starts to clean the cactus spines with a wet cloth, and then sets off on his artistic journey.
"Painting under the sun for a long time isn't easy," the 21-year old tells me.
"And neither is the plant itself," he adds. "I have to remove the spines before I start painting. It has to be cleaned in a way that doesn't hurt the cactus; there should be a good relation between me and the cactus. I need to be patient while working and the plant has to be patient as well, because it will take me a long time to paint on it."
Ahmad says he came to the idea of painting on cactus plants last winter, when he was searching for a way to express his feelings on the Palestinian issue. He tells me it's an issue that everybody has a differing opinion on, but that as an artist he needs to express what he believes -- and in his own unique way.
"The cactus is a plant that lives a long time and it can live anywhere," he says. "And that makes it a human symbol, a symbol of resistance and patience. This is a human art that can spread out to all people."