I have lined baskets with visqueen, a layer of gravel, then another liner of visqueen with slits or holes cut through the bottom. So, similar to a gravel sandwich. No water exits the basket and the gravel and 2nd lining of visqueen allow drainage. A top dressing and some moss hide the upper edges of visqueen.
This worked pretty well for me. I used them outdoors, sitting around in the gardens. Haven't done one in a while though.
