Combine dry ingredients into a medium-size mixing bowl.

Slowly add the vinegar or lemon juice if using and stir in well. (the vinegar will bubble some as it reacts with the washing soda).

Add in the lemon essential oil and continue mixing until well combined.

Press the mixture firmly into each mold with your thumb until it's well compacted.

Allow the pods to harden for at least 24 hours before removing them from the molds.

Store in a cool, dry place.