Alright, so let's start by cutting the 12 blocks of the inner section. They don't have to be really fancy, as most of it will be staying inside the box.

Now that we have the inner sections ready, its time for us to measure and cut the top and the bottom blocks that will be holding these inner blocks. Next, we are going to cut the 8 x 51.5cm blocks that will be holding the box from all the 4 sides.

After spending few hours I finally have all the blocks ready. Now, its time to join them all together.