Do you want to fill the volume with rectangular blocks that already exist…
or
Do you just want to split the final shape into blocks that you can then make and glue up?
I would go with the second option as this is much easier. I did something similar on this project…
BISON specifically this topic where I split a shape into smaller, more manageable parts.
You could do something similar, where you split your final block into smaller blocks that you then make rather than trying to do a complicated 3d nesting / tessellation.