How many do you have? First of all Ducks are prone to just drop their eggs wherever they are when the urge strikes unless they have begun to go broody and/or it is breeding season. At that time they will try to build nest, usually on the ground, and when their eggs go missing they will start trying to hide the eggs from you. Secondly ducks tend to be creatures of habit. The will follow a certain routine and will, in fact, wait for you to fulfil your part of the function before they start theirs.
Example: I have 16 Cayugas that have a large overnight house as well as a sizable enclosed run with kiddie pool, shaded shelters, etc. I take them out into a large field so that they can eat bugs and grasshoppers and use a long stick to herd them. The will follow where I lead and when I click on the stick twice they know that means it is time to go back to their run, turn about and run/waddle back to be locks inside again. Then at about sunset they know (from habit) it is time to go inside their house for the night. I open the gate that lead to the door to the barn that they have to go through to get through another door into their secure house. I then tap on the guide stick twice and they waddle through all that maze, 2 abreast in a neat little line into their home for the night. Usually when I let them out in the a.m. there are 14 eggs scattered about inside their house. Sometimes there will be a late layer but I have figured out where they lay outside and can easily gather their eggs that way.
My Khakis and Blue Swedish do essentially the same thing just in smaller numbers since they are smaller flocks. Each breed has their own overnight space, they know where to go and go there.
I know that this is nothing unique or special since I learned to do it when I was just a kit some 50+ years ago from my grandfather and everyone else around us that had ducks did the same thing. It does require patience and developing the same pattern over and over until they learn it but it does work.
If you are free ranging in a much larger area you are going to have a greater distribution of hidden eggs so you want to encourage them to lay in their house at night. That should not be a real problem since ducks tend to be night layers to begin with.