Make the lye water. Measure out the lye and water in separate containers using a digital scale. Carefully add the lye to the water and stir until it is fully dissolved. The water will become cloudy and will shoot up in temperature. Set aside to cool in a safe place.
Melt the oils. Measure the oils separately, then combine them in a large pot. Melt the olive oil and shea butter over medium-low heat until the shea butter is fully melted. (You may find it helpful to soften the shea butter in the microwave first, as it's slow to melt.) Set aside to cool.
Stick blend to trace. Once the lye water and oils have both cooled to about 100-115 degrees, it's time to blend. Get out your soap molds and any fragrance or color you'll be adding. Pour the lye water into the pot with the oils and blend with your stick blender until you reach trace. Add fragrance and color if using, and quickly pour into the soap mold.
Cure and unmold. Allow the soap to cure in the mold for 24-48 hours, then carefully remove it. Store in a well-ventilated place and let it cure more for at least 3 weeks before using.