So when reading kanji, how do you look up a word (picture) you don't know? Since there isn't a minimal set of characters, the notion of "alphabetical order" seems impossible. Weird that I've never thought about this until now, but I'm honestly baffled.
Also note that on the site linked to common kanji have a red background. Many of the characters are obscure so radical + stroke count narrows done the choices to very few kanji.
Better to have instant dictionary lookup if you're on the phone or laptop than a regular paper dictionary.
Firstly, unusual words tend to have furigana, which makes it trivial. Next, if the unknown kanji isn't the first one in the word, it's possible to do a prefix-based dictionary lookup. In many cases, also, I've been able to guess a reading by common structure. E.g. both 赤(red) and 跡(traces, remains) have a "seki" reading due to a common element, and 根(root) and 痕 (traces, remains) have a "kon" reading, also due to a common element. You might be able to guess at 痕跡 (konseki) by thinking of 根赤.
How we can find 跡 in the Kokuko Jiten's appendix is by counting the strokes first: 13. Then in the 13 stroke section, of the appendix, we find the subsequence of 13-stroke kanji that have the 足 seven stroke radical. The radicals are sorted by stroke count also, so we can find this subsequence fairly quick.
I can recognize quite a number of words that have at least one kanji which doesn't occur in any other word that I know. I've never studied the kanji in isolation, but I can recognize it in that word.