When should I teach children that there are lots of ways to spell sounds in words?

As soon as children start asking how to spell words that are more complex than words such as cat, dog or pig. In other words very early! Teach them to sound out the words (break the words into single sounds) such as b-u-nn-y (for y say ee). That’s enough at first and then slowly teach that there are lots of ways to spell the ee sound, 12 or more in fact!