Self-watering containers are different from regular containers that you’d plant in. The main reason is that the water is sucked up by the roots from the bottom of the container.
They made up of two containers of the same size called a reservoir and planting container. I usually use two food-grade 5 gallon containers.
Inside of the reservoir container, you place a wicking basket with small holes in it. For that I use a 1/2 pound deli-container. There is also an overflow hole drilled into the side of the container to allow for drainage.
The planting container has a 3 1/2″ hole drilled into the bottom in the middle and a 1 1/4″ hole drilled along the edge. It’s placed inside of the reservoir container with the deli container centered. The pipe is then put through the smaller hole down to the reservoir container.
You fill the wicking basket with wet soil and continue to add moist soil to the planting container along with the plant. You water the self-watering container by pouring water into the pipe, which will allow the water to get down to the reservoir container. When the water reaches the top of the reservoir, it will begin to come out of the overflow hole.
Since there are holes in the wicking basket with the soil, it will soak up the water and allow the plants roots to drink up the water as needed. This is a more natural way for the plants to soak up water as opposed to watering them from the top.
It also makes it easier to never over or under water the plant because you can tell by the overflow hole.