Bath melts are tiny solid cubes of oils that stay solid at room temperature, but gently melt into a warm bath, enriching the bath with moisturising oils and fragrance.
1) A saucepan
2) An ice cube tray or suitable small moulds
3) Kitchen scales
Gently melt the cocoa butter over a low heat. Once just melted add the sweet almond oil and mix thoroughly. Remove from heat and leave to cool a little (not too much, it still should be liquid). Add colour and fragrance as required (the equivalent of a few drops of essential or fragrance oil per melt. Colour can be added a little at a time and stirred/whisked (hand whisk) to achieve enough depth. Remember, once set solid the background colour of the cocoa butter will be opaque off-white). If you are using ultramarines or oxides to colour, be sure the mixture is fairly cool before adding them, or they will not disperse. Insoluble Pigments will add colour to the oils whilst they are still warm/hot.
Once cooler but still completely liquid, pour into ice cube tray moulds (or similar) and cool in the fridge or freezer. Don't actually freeze them, just ensure they are very cold and completely solid.
Press out of ice cube moulds as you would an ice cube and leave at room temperature.