Combine the baking soda and 1/4 cup of warm water in a small bowl. Stir until a smooth paste forms.

Combine the castile soap, remaining water, salt, and vinegar in a larger mixing bowl. Whisk to combine. You'll notice the mixture starting to thicken.

Gradually add the baking soda paste to the soap mixture, whisking or stirring continuously until well incorporated. The mixture will continue to thicken as you add the paste.

Add your desired essential oils, starting with 15 drops and adding more to the desired strength. You can use a single oil or create a blend.

Using a funnel if necessary, carefully pour the dish soap into a reusable soap dispenser. If the mixture seems too thick, you can add a bit more water until you reach your desired consistency. Give it a gentle shake to combine before each use.