You can use any scent of castile soap. We prefer the Unscented Castile Soap from Dr. Jacobs since it's unscented. Baking Soda can be picked up from just about anywhere, any kind will do. And for the bar soap you can use any kind you have on hand or that you can pick up from the store (or even Homemade Hand Soap). Remember that if you pick a scented bar soap your homemade Dish Soap will also be scented.

In a large bowl (I have a special one that I save specifically for soap making so our regular dishes don't taste like soap!), add the castile soap, baking soda, grated bar soap, and a few drops of essential oil (if desired). Slowly pour the very hot water over the ingredients in the bowl. Mixing as you pour. (You may need a helper for this!)

Stir until all the ingredients are dissolved. Leave the mixture sit on the counter until it's cool. Stir as needed if you find some parts haven't completely dissolved. Add to a container. I've put together this cute liquid soap dispenser using an old ball jar and one of these Mason Jar Soap Pump Kits.