Thank you, Ctcarol!
Waldeburg,
Once you set your "platform" for the reservoir, be it a colander or tubs, or whatever is holding your soil up, you want to drill the drainage hole approximately 1" to 1.5" BELOW the top of the platform, so the water drains out BEFORE it even reaches any of the soil sitting on top of the platform.
This creates the airspace between the water and the soil. Like Ctcarol said, having the soil sitting directly in the water at all times, or no airspace, creates an anaerobic situation whereby your soil stays wet all the time. And, in this (moderately) closed system, that makes for funky soil and poor plant health.
Hope this helps!
Linda
P.S. Post some pics of your progress, if/when you can!
Hugs!
