This is an example of knocking off flakes from a chert core. The basic idea is to use a hammerstone (shown on the left) to hit the chert cobble with enough force to knock off a flake from the outer surface. The hammerstone should be dense.
The result of knocking flakes off the core is shown below, you end up with pretty random flakes and the occasional blade
You can see I have hit the core lengthwise to produce these few longer blades.
These blades can now be modified some more into refined tools or used as-is.