Shred the bar of Soap. I have found the easiest way is to use a heavy serrated bread knife and shave the soap- it only takes a minute this way and less mess. You can also shred the soap with a box grater or food processor with shredding disk.

Place shredded soap in a large stockpot. Add 1 Gallon of water and heat on stove over medium/low heat until all the soap pieces are melted.

Remove from heat- stir in glycerin (if using) at this time. It will be very thin and watery. Cover and allow to sit at room temp about 24 hours- you will see it turn white and thick.

At this point, you can just whisk in essential oils to your preference and use as is, but I highly recommend blending-- either by doing batches in a blender or food processor or my preference, using an immersion blender. This emulsifies it and makes it smooth, silky and creamy and it wont be "stringy" or "congealed" when using. I will blend it, fill my bottles, and it stays creamy for a long time.

Store the remainder until ready to use. If has been a long time I will usually quickly re-blend it before filling my soap dispensers.