Now, I’ve seen videos of people making this cut then pulling the jig back through the blade with the box still in the jig. I use to do this until the box shifted once and basically ruined that project. So, after I slide the piece through the blade, I left the box off and slide the jig back the front of the table top.
After I move the jig back to the front, I flip the box forward and place it back in the jig to make the cut on the next corner. I do this for all four corners.
Here you can see the kerf left by saw, nice and clean. A flat tooth blade is really the only way to go. I have an ATB+F blade I picked up from Lowes, it works great.