I've set up a 'kiddie pool' as a duckweed pool. I'm feeding it water, comming out of the swirl filter. The 3/4 inch pipe goes to the bottom. I drilled 2 small holes in the side of a slip cap, just enough for a slow flow of water.
The drain is a slo-drain, picking up water from the bottom, so the duckweed will stay in the pool.

Not real fancy....but the pool was 'free'....