I do it this way. It is a time saver, because the hot lye water melts the hard oils. I do try to cut up my large chunks of hard oils, so they melt faster. By using the natural heat created by the lye mix, I don't need to use electric to heat up the oils. I just mix up my lye water, and once it is completely dissolved, I add it to the oils. In a few minutes everything is melted down. Many years ago when I first started making soap, I would heat up the oils, and then mix the lye water, and have to wait, and wait for everything to get to the right temp. Time is money, when you are in business, so anything I can do to save time is helpful.