if u have every seen the TV commercials for that water ball thing, its all colourful and what not, basically u just need a makeshift one of those, just take a water bottle with a hole i nthe top to fit a straw or a tube and seal if off, then stuck the waterbottle upside down and put the tube in the water, as air if released into the bottle from the soil drying up it will slowly release water into the plant pot