Like homeopathy and cell salts, the Bach flower remedies work on the etheric plane. Yes, I've used them -- they were recommended in one of the occult study courses I took -- and they certainly work. I don't happen to know how Bach devised them, but my guess would be clairvoyance; you might see if you can find a biography of him to doublecheck that. If I recall correctly, quite a few other flower remedies have been introduced since Bach's time, and you may be able to find out the method by researching in that field.