There used to be someone selling them on ebay so you could perhaps look at how they had done it. You can buy the plastic nest inserts from Solway Feeders, or you can just have a sloping floor with some old carpet on it. Then just make sure there is a covered area (with a lifting lid) for the eggs to roll into
Put straw and a dummy egg in when they are first introduced to them and as they begin to use them to lay gradually remove the bedding so the eggs roll
Don't forget to nail a bit of sack or cloth over the entrance as the dark helps prevent egg eating
Are they getting sufficient limestone /oystershell grit and protein, shortages can encourage egg eating, as can insufficient clean water.
All the best
Sue