The most common way to explain uncertain kanji is to use another reading of the kanji. For example, undrentide-san mentioned about 湖沼学（こしょうがく） in
the thread "Should Japan Abolish Kanji?", which mdchachi-san linked above. This is an uncommon word, but it's easy to show the correct kanji of こしょう by saying みずうみ and ぬま. Furthermore, みずうみ and ぬま explain the meaning of こしょうがく quite clearly and easily.
As grapefruit-san wrote in the thread, usually the kanji can be interpreted from the meaning of the word which is provided by the context, so this method is often used for proper nouns such like people's names or location names.
When I participated in a Buddhist memorial service, we were talking about three women who had the same name in our relatives. They had married our relatives and changed their names, so they became the same name as a result. When explaining their given name なおこ, I said the first one was 和尚さんの「しょう」, the second was 直角の「ちょく」, and the last was 菜の花の「な」に稲穂の「ほ」. (The last one was the youngest, so an old aunt said "she is young, so her name is the most "fashionable(しゃれてる)".) I think this might be close to a way to explain spelling of a word/name in English, e.g., "N for November" or "P for potato."
Even when the kanji itself is uncertain, a method to explain the components of the kanji is more commonly used. One day, when I made out a receipt, I asked the customer's name. They answered their name あさひけんせつ. I asked about the kanji of あさひ with saying "Is that あさひ of 朝日新聞?". They said "It's きょくじつの「きょく」", and continued "漢数字の「九」に「ひ」です" as an additional explanation. They might think きょくじつ（＝旭日） was not an easy-to-understand word, so would add another explanation. There are many homophones for ひ, but it's easy to interpret that it refered to 日 since we were talking about the kanji of あさひ. Plus, there also was no necessity to explain the right position of 日 (not the lower side of 九, not the right side of 九 completely apart from it, etc.) . This is because we both understood that we had knowledge about kanji.
Sorry for nitpicking, but "having an election" is "senkyo(選挙)." "Sentaku(選択)" means choice/selection in general.
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