Flintknapping or generally knapping is the shaping of conchoidal fracturing stone through lithic reduction with this you can manufacture stone tools / flat faced stones required for masonry. The Term knapping comes from the Germanic "knopp" wich means shape or work so it could mean more than just shaping tools/flat Stones. For manufacturing Stone Tools chert is worked with a fabricator such as a Stone to remove lithic flakes from a core of the tool stone. The finished Tool stone then can be pressure flaked using bones or wood and antlers. For building work a hammer or pick is used to split chert nodules wich are suported on the lap. Usually the chert nodule will be split in half to create two cherts with a flat circular face for use in Walls. Advanced knapping is employed to produce very good Cubes wich can be used as Bricks.

You can use many tools for knapping like wood hammers or antlers from animals. In order to remove large flakes of stone it is possible to use cobbles of very hard stones. This way it is possible to make small tools. This is known as the first method of manufacturing stone tools for around 2 million years

How we could use this ingame: We could shape stone tools with knapping them into the right shape for example stone hammers, shovles, knifes and also stone decoration.

Sources : Various Knapping Websites

A correction it's a Cuboid that's the shape of a Brick not a Cube.

You can make Bricks out of mud and clay btw..

Also, flint is quite common, look in your local area if you find a dark rock that's sort of shiny (if it's broke) then that's flint.