1. Measure and mix your baking soda and citric acid in a large bowl. I used a metal mixing bowl because oils can be absorbed by plastic. I’ve never had that experience personally, but if you’re worried about it, go for metal or glass – something non-porous. 

2. Add your water slowly, a little at a time and begin mixing with your hands (you can use a spoon if you like, I just find using my hands works better). It’s going to fizz. That’s normal so don’t panic. Once you’ve added all of the water and gotten it incorporated (it should still be on the dry side, but clumpy) 

3. Add your essential oils (you can totally customize the strength of the smell. I would start with a drop or two and then add more if you want a stronger scent) and get your hands in there once again to incorporate the oils into your mixture. 

4. Fill your molds and let them dry overnight. You’ll probably notice it will feel kind of tacky while you’re putting it into the molds, but it shouldn’t stick to your fingers. 

5. When dry, gently remove them from your mold (it shouldn’t need much force) and pop them into a waterproof container. 

6. When your drain needs freshening, drop one in the drain and run the warm water! It will fizz a bit and break down and you will have a yummy smelling drain and kitchen. Try customizing the sent with a different blend of essential oils such as lemon & thyme or tangerine & lime.