An "empty slot" refers to a space or position that is free and available, normally used to describe a vacant spot in a schedule, a missing object, or a job position that needs to be filled. Full definition
It will help you fill empty slots with people for whom the reality of summer at home with the kids is sinking in. (sportstarsmag.com)
A summer sale could make the decision easier for them, while filling empty slots for which you would otherwise get nothing. (sportstarsmag.com)
What's more, companies often end up wasting a lot of resources on marketing campaigns to fill empty slots when a lower - cost in - house scan might prove more effective. (inc.com)