Being summer will encourage them to lay sooner...if it was winter you might have to wait for the daylight hours to start. In my experience, ducks have a tendency to lay just about everywhere but having 'starter' eggs (whether chicken eggs or just ceramic eggs) in a nest where you want them to lay will encourage them to favor that area. I've used straw, hay, shavings, gravel, and bare ground for my ducks (erm, actually that's what was in the coop that THEY decided to use! Except the one who laid every single day in their pool...goofy bird!) Mine seem to favor setting up nests in narrow areas with high 'ceilings' like between the dog house they were supposed to be laying in & the side of the pen. Or between the nest box in the coop & the side of the coop.