I raise 12 or less ducklings at a time when they're to be raised indoors (winter). The first week, I have them in a big plastic tub with soft bedding. After the first week I move them into the bathroom in the bath tub. A doggie pad is used on one end under a light while the other end, where the feed and water are, is bare. Daily the tub is cleaned by removing the pad, turn on the water, rinse, scrub, and rinse again. As the ducklings get bigger I let them swim, dive and clean themselves. The tub is drained, wiped, and a new pad put down. I find this a lot easier than anything else I've tried. Yes, it does get smelly, but not as bad, and the cleaning is a whole lot easier. When the ducklings are three weeks or older, depending on the weather, they are moved outside. In 3-4 weeks the ducklings have developed enough body fat that they easily withstand our winter temps. I've often seen them splashing/playing in their kiddie pool when the outside temperatures were just above freezing!My ducks don't sit sadly. Use electric incubator.
There's afew chook people over here whose hens only sit at night but the eggs hatch perfectly because the daytime temp is around 100f (38c). Feb heat waves, when ducklings would be in a brooder are anywhere between 104f (40c) to 118F (48c) I could bring them inside but stinkly ducklings inside for days on end....