I was there - having saved a large quantity of spent soap nuts to turn into liquid soap at some point in the future - the box was dug out and added to a large pan along with a couple of spigs of rosemary and the left overs of a juiced lemon.
All the ingredients were free!!! what ever happened I had lost nothing except a few minutes of electricity.
I brought the pot to the boil then let it simmer for 10 minutes before turning the heat off and leaving the mixture to cool. Once cool I poured the mixture (pods/ rinds and all) into a nut milk bag and hung it on a cupboard door handle to drain into a large jug. Once strained I popped the mixture into a cleaned bottle I had retreived from the recycling box. A funnel helped the speedy bottling process and my love of glass painting helped label the bottle.
I felt the soap did not quite smell as citrus as I had envisaged (although it smelt great when it was simmering) so I also added about 10 drops of grapefruit essential oil. It smells lovely. The only problem is that I am keeping it in the fridge - so everyone things I have gone bonkers and am playing hide and go seek the bubbles!!!!!
Have a go - it is great fun, simple and a great way to use up spent soap nuts :0)