Put the flour into the bowl.

Cut a cold stick of butter into small cubes. Add the butter to the flour.

Use a pastry blender (or a fork) to push through the butter and cut it into smaller pieces. Result will be better with pastry blender.

Keep pushing and rocking the pastry blender (or a fork) against the bottom of the bowl through the flour.

Keep working until the butter clumps are at least as small as small peas. Now it is ready to use.