No, I don't mean the effect of brussels sprouts on your digestive system! These are NICE smellies.
Bath melts (recipe for 12 small ones):
Six tablespoons of coconut oil, melted at a low temperature
10-15 drops of your chosen essential oil (can mix more than one)
Allow the mixture to cool a bit but not enough to solidify. Shape using ice cube trays or chocolate moulds. When fully cooled, place in the fridge and leave there for a few hours. Store in the fridge until wrapping, warn recipients not to leave them near heat sources.
Bath salts (recipe for 2-3 jars containing about 3 baths worth)
Mix a large-ish quantity of white rock salt, a slightly smaller quantity of coarse pink salt and an even smaller amount of fine pink salt. (Or of course you could use all rock salt - make sure you get some of the finely ground stuff too though)
Drip in 10-15 drops of essential oil (fine if it's a bit strong at first, it runs the risk of fading)
Divide into the clippy jars. They aren't the most visually appealing packaging but can be repurposed in their new home once the salts have been used. Or you could do your own repurposing and use jam jars.