To take a concrete slump using a slump cone, follow these steps:

1. Gather the necessary equipment: You will need a slump cone, a base plate, a tamping rod, a ruler, and a measuring tape.
2. Set up the equipment: Place the base plate on a level, stable surface. Position the slump cone on the base plate, ensuring it is centered and firmly held in place.
3. Prepare the slump cone: Moisten the inside of the slump cone with water. This helps prevent the concrete from sticking to the cone.
4. Fill the cone with concrete: Carefully fill the slump cone in three equal layers. Each layer should be compacted with a tamping rod 25 times, ensuring that the strokes are distributed evenly over the cross-section of the cone. Continue adding concrete until the cone is completely filled.
5. Level the concrete surface: After the cone is filled, use a trowel or straight edge to level off the surface of the concrete. Remove any excess concrete from the top of the cone.
6. Lift the slump cone: Hold the slump cone firmly by its handles and lift it in a vertical motion, taking care not to disturb the concrete inside.
7. Measure the slump: Immediately after lifting the cone, place a ruler or measuring tape adjacent to the cone, touching the top surface of the concrete. Measure the distance between the top of the cone and the displaced center of the concrete slump. This distance represents the slump value.
8. Record the slump value: Take note of the slump value in millimeters or inches, depending on your preferred unit of measurement.

Here is a step-by-step guide with corresponding pictures for a visual reference:

Remember to follow proper safety precautions, such as wearing protective equipment, when working with concrete.