Gently shake the elderflowers to remove any dust, insects, or fertilizer.

Place the elderflowers in a large heatproof bowl or pan with a lid.

Add the thinly sliced lemons to the bowl.

Add the white sugar to the bowl.

Pour the boiling water over the ingredients.

Add the citric acid to the bowl.

Stir all the ingredients together until the sugar has dissolved completely.

Ensure the lemon slices and most of the elderflower heads are submerged in the sugar water.

Cover the bowl or pan with a lid.

Leave the mixture in a cool place for 4 days to infuse.

Each day, remove the lid and stir the mixture.

Gently press the lemon slices to extract the juice.

After 4 days (or 5 if needed), strain the mixture through a non-metallic fine sieve, lined with muslin if necessary.

Pour the strained cordial into a large pouring jug or bowl.

Pour the cordial into clean and sterile bottles.

Seal the bottles tightly.

Store the cordial in a cool, dark, dry place for long-term preservation.

Dilute to taste with water or add to other beverages or recipes.