Check out the size of these foams and double-wall carton. They are thick and big.

A closer view to see the double-wall.

After removing one screw at the center rear location of the top plate, the entire top plate can be easily removed by sliding toward to the back of the case.

After the top panel is slide off and take away, you can see the handle plates for each of the 2 side panels 

The handle plate for the side panel is located at the center as you can see on this picture.  Gently lift it up and the entire panel can be taken away easily.

As you remove the side panel off the first time, you would notice that the case is constructed with a high quality metal panel on the inside and an industrial grade plastic panel on the outside.