Do any body have any experience in making your own carbon filter?

If you want to make a really good filter, you can do something like this, however, multi-layer it and use different weights of activated carbon. Start with a larger grit, medium grit, and the a fine grit in the center. Micron screen / filter papers work well for this. Entirely plausible and you have the working concept correct. Might wanna go more like 5cm to get adequate surface area/air flow.