Here is another idea.
Leave the planters as they are with the fabric liner, but put a liner of a heavy gauge clear polyvinyl (plastic) on the bottom and up the sides so it is watertight. Then, keep the plants you are using in their plastic nursery pots and have them sit in saucers inside the box. Cover the top with a top dressing of Spanish moss to disguise the plastic pots.
This will prevent any leakage and allow you to water each plant individually and also replace them individually, if necessary. The Spanish moss is light enough that it is easy to pull aside to see inside the box and make sure you are watering properly. It also means you don't have to disturb the roots of the plants you are using.
