Wash and dry the egg shells thoroughly to remove any residue.

Use a rock or mortar and pestle to grind the egg shells into a fine powder. Ensure there are no large pieces remaining.

Transfer the eggshell powder to a dish for easy mixing.

In a separate dish, measure and combine the flour and very hot tap water. Stir until a smooth paste forms.

Gradually add 1 teaspoon of the eggshell powder to the flour and water mixture.

Mix and mash the ingredients together until the mixture sticks together and forms a pliable dough.

Shape and press the dough into a chalk-stick shape. You can use your hands or a mold.

Roll the shaped chalk stick tightly in a strip of paper towel to help it maintain its shape and absorb excess moisture.

Allow the chalk to dry for 3 days, or until it becomes hard as a rock. Ensure it's completely dry before use.

Once dry, remove the paper towel and write with the chalk on a chalkboard or other suitable surface.

Erase the chalk marks with your shoe or a chalkboard eraser.