This isn't a cardboard or paper mache knock off this a solid plywood shield, 45 inches in diameter weighing in on just over thirty pounds. So if you are looking to make a disposable prop i suggest you look elsewhere. It is easy enough to make and only cost me 15 dollars from start to finish.
Step 1: The Base
If you want to make the same size i did i suggest you start off with a 4 foot by 8 ft piece of plywood, the thickness depends on how strong you want it 7/16 in worked for me. Once you lay the board on a sturdy surface and clamp it down. You are almost ready for cutting but first make sure you have proper eye protection and gloves to protect your hands from splinters. Using a jig saw cut the board in half making it into two 4 by 4 boards.
Now you want to draw a circle on one of the boards. This is the first ring of the 6, 3 rings from each board. The first ring should be significantly larger than the rest to give it the spartan shield look. I used a nail, string and a crayon. Placing the nail in the center of the board i tied one end of the string to the nail and the other end to the crayon. Keeping the string tight i move the crayon in a circle.
Once you have your circle a drill a small hole somewhere along the line and place the jig saw in the hole and saw along the line.
Step 2: The Second Ring
Once you finish the circle remove the inner circle. Then take the other board and place the outer circle you just cut and place it on the board then trace around the edge of the wooden ring using a crayon. Then using the nail string and crayon make a smaller circle by a about 6 inches. Once you board as both circles drawn on it use the drill to make a small hole on the inner circle and cut around the inner circle.
At this point you should have two wooden circles one 12 inches smaller than the bigger one. Place the smaller circle on top of the bigger one and trace around the circles edge with a crayon. Remove the smaller circle and use the nail string and crayon to draw a 2 inch smaller circle than the one you had just drawn. Drill a small hole in the inner circle and place the jigsaw blade inside of it and cut out around the crayon circle.
Now you should have 2 circles and one ring, place the ring one the ground and place the larger circle on top of it and the smaller circle on top of the that one. The rings don't have to be perfect since you can cover it later with a canvas.
Step 3: Build the Pyramid
Then trace around the smaller circle with a crayon on top of the bigger circle. Take the bigger circle and using the nail string and crayon draw a smaller circle 2 inches inwards and cut out around the inner crayon circle. Once you have sawed out the ring once again place the bigger ring on the ground and place the smaller ring on top of it and the bigger circle goes on top of the ring and the smaller circle goes on top of the bigger circle. Keep repeating this step till you have 4 rings and 2 circles.
Now place the smaller circle on the ground and the bigger circle goes on top and pile on the smallest ring and follow it up with the second smallest then the second biggest and finally the biggest ring on top of that. Now it should look like a upside down pyramid.
Step 4: Connect the Rings
Now take the drill and start drilling in screws on each ring so that each ring connects to the ring under it without the screw going all the way through the ring under it. It is good to first find the perfect size screw for this task and using as many of that same type of screw as you can.
Once you finish screwing in on all the layers you should be able to pick it up without out any of the layers falling off. Make sure each layer is securely attached to the layer under it.
Step 5: The Handle
This is the simplest type of handle you can make. It is simply two straps of leather that i got from a broken belt and screwed them in so that i can securely hold the shield by reaching my are through the larger loop and grasping the smaller loop with my hand. The fabric is screwed in for your arms comfort and other than that has no real use.
Step 6: The Canvas
You can use what ever fabric you would like for this part but if you plan to paint over it i suggest you use a light colored burlap material. If you want to keep it bare wood or use decorated fabric that is up to you, but i liked how it turned out with the paint.