Spoon the wax of choice into the jars. Using the back of a small measuring cup or large spoon, press the wax down into the jar as it gets closer to the top. Add more wax until the jars are full. At this point, you'll probably only need about 1 cup of wax per jar.
Place the filled jars in the slow-cooker base. Turn the slow-cooker on high. Add boiling water to the slow cooker, until it comes halfway up the exterior of the jars.
Allow the jars to “cook” for 30-45 minutes, covered.
After 30-45 minutes, the wax should begin melting. Add more wax, pressing the wax down with a small measuring cup or spoon until full. Place the lid on the slow-cooker and "cook" the jars for another hour or until fully melted (soy melts quickly, beeswax takes longer to melt).
Carefully remove the jars from the slow-cooker using a hot pad holder or a towel. Let the candles rest for 10 minutes.
For Fragrance: If you'd like to add an essential oil, in a small bowl, stir together 1 tsp of liquid coconut oil and 50 drops of essential oil. Pour the mixture into the candles and stir. If you're using fragrance oil, no coconut oil is needed--follow the instructions from the supplier.
Place one wick in each jar, holding up the tops of the wicks with clothespins or mechanical pencils or pens using the clip portion. This will keep the wicks from moving in the liquid wax.
Let the candles rest until cool and solid (about 30 minutes).
Once cool and solid, cut the top of the wicks to 1-inch. The candles are ready to use. If any holes appear at the top of the wax (this can happen when the candles cool too quickly), melt more wax in a separate jar and pour into the holes to fill. The holes are just a cosmetic issue.
Notes
The number of candles you can make at one time will depend on the size of your slow-cooker. My slow-cooker fits 5 4-ounce jars.
Servings: 1candle (make as many as desired--see notes)