If you only have two fake eggs, put them in the nest boxes that are used most often. Some hens lay in the morning, and some later in the day. Since yours just started laying I would recommend checking the nest boxes first thing in the morning, then early afternoon, then at night when you lock them up or whatever your nighttime ritual is.
If you do have a potential egg eaters, checking more often will allow you to remove temptation and actually get eggs. But if you have hens who keep getting disrupted because you are checking too often that could impact their laying. I think it's kind of a play it by ear situation.
