Customize flyspell (ispell) dictionary

I know how to add custom words to ispell, but I would like to remove certain words from the dictionary. For example, although ass and asses are correct words, I rarely type them, and would like to flag them as likely typos to as and assess. Where does ispell store its dictionary? The man page does not provide the location. Also, the man page makes it seem like there are a lot of steps to build a new dictionary, and it isn't just an ASCII file where I can remove certain words. Any advice how to build a new dictionary without a given word? **Edit** From some hints on: http://docstore.mik.ua/orelly/unix/upt/ch29_05.htm It seems like I can start with /usr/share/dict/words, remove the words I don't want, and then make a new ispell dictionary from that. However, I'm having trouble making the new dictionary. buildhash is the key program here, but it wants an affixfile, and I do not know how to generate that file.