Step 1: Ingredients & containers
1 1/2 cup epsom salt
A few drops of food coloring (preferably the gel type)
1 tsp jojoba oil
1/4 tsp essential oil
Epsom salt can be found in any pharmacy. It could be replaced with some fancy schmancy dead sea salt, but really, you might as well flush your money down the toilet... the pricy alternatives make no discernible difference whatsoever, except as a marketing gimmick.
Jojoba oil has a very long shelf life and is well tolerated by practically everybody -- but it can be replaced with a number of oils including grapeseed, avocado, sweet almond, or even mineral oil.
Essential oils can usually be found in health food stores (even though they are NOT to be eaten!) and sometimes in pharmacies. Different oils will give the salts different properties: peppermint and orange are invigorating, lavender is relaxing, eucalyptus is great for head colds, etc. I used to think the various healing qualities of essential oils was about as serious as horoscopes, but I have lost some of my skepticism since I've begun experimenting with them. They won't heal you, and should not be considered a cure or medication, but different scents will definitely influence how you feel.
The container can be any recycled clear glass or plastic jar with a proper air tight cover. The containers I used in the intro picture were made from a clear plastic tube (designed to cover fluorescent lights) I bought from a hardware store, then chopped into pieces.