Put it in a box or enclosed cage with a very powerful lamp.
you could put them under a broody chicken. it may not work but you could try a heat lamp, they need one once they hatch anyway.
An incubator.
Duck eggs should be kept at a temperature of around 99.5°F (37.5°C). This can be achieved by using an incubator or a broody duck for natural hatching. It's important to maintain a consistent temperature throughout the incubation period for successful hatching.
Put it in the fridge. If you are hatching it, then use an incubator.
incubator which is like a hen sitting on the eggs and the incubator keep the eggs nice and warm and moves them like a mama hen would do but a incubator cost a lot of money
they use their stomachs as an incubator to keep the eggs warm enough to hatch properly without defects.
Eggs are spaced apart in the incubator to allow for the circulation of air. It is also important to keep a space between the eggs so that there is room to turn them over periodically.
Use a heating pad, and keep it on low. Cover the heating pad with a towel. the eggs should be turned over on the opposite side twice a day. once when you wake up and once when you go to bed.
Duck eggs that have baby ducks inside can only last around 60 hours in the cold without being incubated. If they have no baby inside they can last a long time. Up to a few weeks. But if the egg is left to long then it will go rotten. Check first to see if the egg is fertile, if so transfer to an incubator or under a broody hen. Go to duckeggs.com for more accurate answers.
Eggs will not hatch if they have not been incubated either by a hen or by an incubator. And it's not the chickens that are breaking and eating your eggs. It's snakes, rats, raccoons, opossums and other such animals. I suggest you strengthen your coups defenses or bye/make an incubator otherwise you will never have your eggs hatch out.
Ducks usually incubate their eggs for about 28 days
Yes, turning the egg is natures way of centering the yolk in the albumen as it develops. The egg can be turned more often without ill effects but at least twice per day for 18 days is recommended.