Progress will likely be slow, as I'm not a very good wood worker, and am usually pretty busy. If you're a good wood worker, skip this part. I'm going to try and help other newbs out. Most of my clamps are 24" and this box is just large enough to make them useless, so I decided the glue/screw approach would work.
My method was to dry fit the panels, and adjust for squareness. I used clamps with light pressure to keep things aligned.
Once I was happy, I drilled pilot holes (3/32" bit) through the vertical pieces to prevent splitting, and to align everything. I marked to corners with letters so there would be no confusion.
I drove the screws thorugh the top/bottom panels just enough to grab the pilot holes.
Glue (PL Premium) was put on the bottom, a panel set on the screws, and then a few of the screws were drove into the piece to hold it. After both side panels were tacked, the top was set on and tacked, and all of the screws driven in tightly
This is the first set of braces, and where I'm at currently. I measured in equally from the sides and drilled holes, then screwed the braces in place. 2" x 3/4" strips of ply.