Fill empty foaming soap dispenser with water, approximately 4/5 full.
Fill remaining space with a liquid soap of your choice (and glycerine and essential oils, if using) being careful not to get too close to the top.
Shake gently to mix and use. Note: you definitely do not want to add the soap first. If you do, the soap will foam up as you are adding the water to fill the container and you will end up with a foaming, half-filled container.
If you are wondering which essential oil to use, citrus oils like lemon or orange are wonderful!