Clean and dry your glass jars. Centre a pre-waxed wick in each jar by tying it to a pencil or skewer laid across the top of the jar. Ensure the wick base is touching the bottom.
Measure out soy wax flakes — you need roughly 1.5× the volume of your jars. Melt in a double boiler or heatproof jug set in a saucepan of simmering water, stirring until fully melted (around 70°C).
Remove from heat. When the wax cools to 60°C, add fragrance oil at 6–10% of the wax weight (e.g. 30ml per 300g wax). Add a few drops of candle dye if desired. Stir for 2 minutes.
Slowly pour the wax into the prepared jars, leaving 1cm of space at the top. Pour at 55°C for the smoothest surface. Allow to set at room temperature undisturbed for 24 hours.
Once fully set, trim the wick to 5mm. Allow the candles to cure for 48 hours before the first burn for the best scent throw.