Hi Mrz, was that a response to my comment? Sight Words is a slightly different thing again, in that you're largely learning the shape of the word from flashcards.
My preferred approach is a slower thing altogether: put the word 'elephant' on your mental whiteboard. Read the letters off as though you were reading off a sheet of paper. Read the letters off backwards: t,n,a, etc. Try it again for a word you find difficult, eg mediterranean. It's too long, so break it down: medi-terra-nean -put it on your whiteboard, read the three blocks off forwards and backwards. You'll never misspell it!
Actually, I think we do do it for every word we use: I tried the word mediterranean in a session with a child, then realised I didn't reliably know how to spell it, so had to learn it together with my client there and then!
In terms of chunking and mapping across to other words, this is very helpful - pretty soon you have a whole collection of prefixes and suffixes to draw on , especially if you take an etymological approach, eg digress, regress, aggress etc.