i agree drilling is the best solution. You don't have to drill the bottom, you can drill one of the sides like a semi hydro pot (one hole though). You can use eggcrate to create a false bottom so your plants don't touch the reservoir of water and avoid using the hydroton which will block the hole you drilled. Use a bulk head to attach a hose for drainage.
Or, you can avoid draining,and create a small corner pond, that is, an area where you can see and access the water with turkey baster and suck the water out when it accumulates too much.
"We must not look at goblin men,
We must not buy their fruits:
Who knows upon what soil they fed
Their hungry thirsty roots?"
by Christina Georgina Rossetti