I recall one person a while back had trouble with the kanji for dawn. the reading was akebono, but he couldn’t remember that, so I had come up with a mnemonic saying that, “I’m sure you know bakemono means monster, and monsters only come out during dawn” When you rearrange and whatnot you get akebono, the actual reading.
And coincidentally, OP was dyslexic and said that mnemonic spoke to him. Thread here
I’m not dyslexic, nor a teacher, I don’t really know how it works, but maybe you could pay extra attention to the mnemonics your student uses, if they can’t remember a certain thing, change the mnemonic to something that could work with dyslexia.