How do I randomly spawn something like (minerals/ore)

Hi, I'm thinking is there a way to randomly spawn a small object such as grass, minerals or ore randomly every x seconds all over the layout. Such as in this image where grass is spawned randomly every few second all over the layout

for every x seconds

- repeat random (y times)

- spawn (create) object (or family of objects - will pick randomly from family) at layer nameOfLayer, x (random 0, layout.width), y (random 0,layout.height)