Take a 24-bit key, for ease of example. Split it into three 8-bit sub keys. Make a list of 256 english words. Assign a word to each subkey.
1101 1000 = chair 1101 1011 = gobble 0110 1001 = stealth
Expand the wordlist or total number of words to fit your use case. I coded something simalar to make a xkcd-compliant random password generator. Took maybe a few hundred lines of code. Too much to totally list here, but I'd be happy to go into more detail off HN if you want.