I've gotten to the point where I'm using quite a lot of liquid castille soap and that cost can really add up. Dr. Bonner's bars are cheaper than the liquid soap so I decided to try my hand at that.
I got out my new grater, a bar of Dr. Bonner's, and a bowl. I have no idea why I keep getting out these small bowls, the shavings always end up falling all over the place. Usually I begin over a bowl then remember I need to do it over my "making stuff" bucket.
Anyhow, grate your soap as fine as you dare. The finer the grating the less you need to worry about making sure everything will dissolve into water.
I transferred my shavings to my bucket then added 10 cups of hot water. Then I used my immersion blender to mix everything really well.
Then wait 24 hours.
It will have gelled up similar to how home-made laundry detergent will.
This way your soap comes out a bit thick. So if you want it much closer to the consistency that it comes out of the bottle just add more water until you're happy with the consistency you now have.
I have to be honest, after using this method I still kinda prefer the liquid I buy. I'll just have to keep trying until I get the results I want.