I think it's called window box art, but I'm only about 70% sure. They probably sell the boxes at any of those craft stores. I've seen boxes like that filled with different colored pasta at Papa Gino's.
my son and I were going to make one of those but using a toy dinosaur skeleton.
We were going to put the bones in a container and then fill the container with liquid acrylic. I wanted to use a decaying mouse but my son wanted a dinosaur instead.