There are flies coming from cracks of my kitchen. They are the slow " stoner flies". I spray bug spray, but then will notice they'll be coming out of another crack. The kitchen is clean. The trash is out. There is no food out. What is the cause & how do we stop it

Usually dead mice in walls, or food decaying in there dragged in by mice. Spray in every crack and spackle over every crack, for what it's worth - it's a never ending battle. Mice can get through a crack the size of a quarter on it's side.