The part that is very difficult to diy is the packing of the carbon.
I think CAN uses a machine to shake the carbon into place and pack it in tight.
I'm curious if you have an idea of how you would achieve a tight filter. Not challenging your ability, just curious.
If you think about the astronomical number of possibie arrangements for each piece of carbon to be, it is a lot.
With each possible arrangement, there is a precise volume that the carbon tightly fits. Achieving that perfect arrangement with household equipment could be tricky. I don't know you though. Maybe you have some McGuyver shit in your sleeve.
If you have loose spots, the effectiveness of your filter is compromised.