The links are working now. It is a side view and the glass top view as well. Before gluing anything you should create your layered materials into a finished block first.
If you plan on using the foam idea above, the canvas cloth covering the layer of cork and foam, you need to pre-cut your foam and cork to the size you need for the shadow box. For best results I find a metal ruler and razor allow much cleaner cuts.
With those cut to size you need to glue them lightly to one another. The best option is a spray adhesive glue, like the 3M Super 77 or this one - I've used other spray glues and they can be hit and miss on quality/stickyness though, but can save money. Often those adhesives are called a general purpose spray adhesive or similar, and are about $5 a can, but should do fine on this project.
Take the cork and foam outside, lay them on newspaper, and spray the glue lightly on the two sides to glue together (spray both the cork and foam). Let the glue sit for a few minutes (read the can directions as they do vary some), then align the cork and form together (sticky sides facing together) and press them together - as you only have one shot at aligning them, start in a corner and slowly lay the material down keeping it aligned as you stick them together. If needed repeat gluing pieces of foam together to get the desired 1/2" thickness.
Next, you need to wrap them in the canvas/duck cloth if you using that too. The easiest method with the best look, would be to let the cloth overlap 1"-2" on the back of the foam after covering the front and sides. I personally would just leave the cloth uncut to ensure it fits properly, and cut the excess cloth off the back. Spray the adhesive onto the cork side (top/front) of the cork/foam block you made, just glue the top and nothing else. Let the glue sit as the directions say on the can.
When it's ready, lay your canvas/duck cloth out completely flat (wrinkle free) on a hard surface, and hold the block above the fabric about 2" from both sides of a corner (allowing for enough cloth to overlap your material). With the block positioned slowly lower the glued block and press it onto the cloth, before the glue sets tight you should be able to pull the fabric a bit to get rid of any minor wrinkles you may have gotten accidentally. Let the glue harden then pull the fabric over the foam onto the back, then using scissors cut the cloth so there is 1"-2" of cloth overlapping on the backside of the foam all the way around the foam block.
Lay the block on newspaper (cloth side down) and unwrap the cloth from the foam block back and sides (leave the front glue side alone), as you will need to glue the loose cloth to the block. Using the spray adhesive, put glue along the foam edge and the foam bottom of the block - just spray a line a few inches around the bottom for the cloth to attach to. If you feel confident in your spray gluing abilities, spray the inside of the cloth that will touch the foam on the back too. Let the glue sit as the directions say on the can. Then attach the cloth slowly, pulling gently to remove wrinkles and pressing it into the glue on the foam. Do that for four of all the cloth sides and your block will be finished.
Finally with the completed layered cloth/cork/foam block you are ready to mount it into your shadow box. Spray adhesive onto the bottom of the foam block (the side with the overlapped cloth). Let the glue sit as the directions say on the can. Then carefully lower and position the finished block into it's location in your shadow box. Your done.
Just go slowly, and be aware of what is getting glued properly, and you should be fine. Of course check with the instructions as you go, but it is much easier project than imagined. It will likely take 30 minutes to 1 hour to do, but once you have figured out how to do something like this, it will only take 10-20 minutes.
