I did this last year and it made a great gift as well as being very practical. I had one jar to gift and one to keep.
The recipe is from another user on Ravelry.com called Knitfrogknit.
From knitfrogknit project page:
DIY Wool Wash
4 cups boiling water
4 cups lux soap flakes (or grated pure soap like Sunlight soap or ivory soap)
Mix well using hand held stick blender
Add 1 cup methylated spirits and 1 Tbsp (25 ml) of Eucalyptus essential oil
Mix again using held held stick blender
It will make a greenish water, leave in a wide mouth glass jar overnight and it turns into a firm white jelly.
To use rub into stains or dissolve 1 Tbsp in warm water, swish or soak garment, rinse well in warm water.
This made 2x jars (Dolimio style jars).