Once you have a solid and complete box you now want to cut out the center so that your main picture with really light up!
Measure in 2" from the outside edge all the way around your box and create a smaller square within the square. This is the piece you will need to cut out.
This step would be easily done with a good hand saw, router, or jig saw but if you only have a circular saw like me, we can still make it work! *Be sure to measure the size of the saw blade so that you can start your cut without the back end of the blade going outside of your measured square.* With the combination of the circular saw and hand saw, cut out the center of your box as seen in the picture. You can use sand paper as necessary to perfect the lines as you wish.