To remove a coffee stain from sandstone kitchen counters, follow these steps:

1. Blot the stain with a clean cloth or paper towel to remove any excess liquid.

2. Create a paste of baking soda and water to form a thick consistency.

3. Apply the paste onto the stained area, covering it completely.

4. Leave the paste on the stain for at least 30 minutes or until it dries out.

5. Remove the dry paste with a stiff-bristled brush or a clean cloth.

6. Rinse the area with clean water to remove any residue.

7. If the stain persists, mix equal parts of hydrogen peroxide and water and apply onto the stain. Let it soak for at least 30 minutes and rinse with water.

8. Dry the area completely with a clean cloth.

Note: Avoid using harsh chemicals or scrubbing too hard on the sandstone surface to avoid scratching or damaging it.