Watering from below is very practical and labor saving if you have numbers of pots. But, pristine conditions are imperative as the slightest outbreak of disease will extend like fire. Nursery plastic trays are not difficult to obtain. Plastic is better than metal as can be more easy and drastically disinfected. Besides, metal is always cool in shade or in sun will roast the pots in it. In watering from below the most difficult is to adjust the proper quantity of water to let them the plants drink without drowning.