While it might look like those grapes are in weirdly-shaped bread, they are really in clay. A pair of clay bowls are made, and left to bake in the sun. When they are dried, they are ready to use.
“When each pair of rustic “earthenware bowls” is completely dried, around 1kg of ripe unbruised fruit are put inside, and then sealed with another serving of mud to form a single closed, air-tight vessel.” Farmizen
This is called a “Kangina” and is an ancient preservation technique still used in Afghanistan to this day.
The kangina are put somewhere cool (sometimes buried) and will remain fresh for up to 6 months. They are both eco-friendly, and effective.
Just a guess here, but it could be one part being in an air-tight sealed container, and one part being stored in a cool location. The porous nature of clay might also be an advantage somehow too.