I made this today, it worked really well!
I love the liquid Dr. Bronner's, but it can get costly. As a result, I would use it pretty sparingly. Then my local grocery outlet started carrying a brand of organic liquid castile soap called Seattle Organics. Seattle Organics was made by Ballard Organics specifially to sell in Grocery Outlet stores. It was $4 for 16 oz, and really great stuff. I didn't know when they were going to stop selling it, so I stocked up. I'm still going through my stockpile and I just found out that they went out of business a year ago :(.
So I started looking online to see if I could make it from scratch, if not, I would just go back to Dr. Bronner's. From scratch seemed like way too much work, but then I kept seeing that people were making it from bar soap!
The most used recipe online seems to be one bar of soap (not just castile, any kind but dove), 1 gallon of distilled water, and 2 T glycerine to thicken it. They were winding up with something that had the consistency of snot, but if you blended it with a stick blender or beaters, it got better. I prefer the consistency of the dr bronners (seattle organics is the same), so I omitted the glycerine. I also used half the water because I didn't want to chance it not being concentrated enough (I can always add water). I used a 5oz bar of Dr Bronners hemp almond.
The results is a half a gallon of liquid soap at a cost of $5. The consistency and strength seem to be just about the same as the Seattle Organics.