Backhoes to clear the path of the sidewalk, road rollers to smooth the rock/stone/pebble base surfaces, pre-manufactured re-bar to cover the base, cement trucks bringing and pouring the concrete, several workers to rough and detail the surface....
The sidewalk is large enough for all the equipment to fit comfortably on it - about 12 feet wide. It is pretty much exactly what you think you will see when any major sidewalk project is being built anywhere...