How to make a 2-liter SIP (sub-irrigated planter)

(from http://greenroofgrowers.blogspot.com/2012/03/lets-make-sips.html

What a great idea! Take a 2-Liter plastic bottle, cut it in half and use little strips of cloth to wick the moisture from water to irrigate your plants, especially if you aren't around to water them yourself. Brilliant! Got a great idea? Share it, por favor!