Sandy, that's how I got the idea. From seeing a manufactured and spendy one that came with much praise and documentation. 20 or so years ago, when I saw this I looked at its construction and made a similar one without the separated compartment near the bottom. Adding vermiculite and perlite to my soil medium helps the wicking process.

I have half a dozen self-watering planter boxes that I hang on our south-facing deck railing to grow flowers in every year; I was never able to keep anything growing there (despite my northerly latitude) until I used them (and was diligent about keeping the water reservoirs filled). I'm sure an argument could be made that "marigolds don't like wet feet, but they always put their roots right down into that water reservoir.

Steve, do you concoct your own potting mix "from scratch," or do you just add more perlite and vermiculite to a commercial mix?

Sandy, I do use a local bagged potting mix. Nature's at about $8 per 2 cf bag. I looks good and is consistent but I do add a scoop of garden lime for raising my ph a bit since it is peat based and we naturally have acidic soils. The vermiculite and perlite give it water holding and tilth.