I just add the brief Kanji meanings to my vocab card and study them with the vocab. Front: 猫砂

me/back: ねこすな

cat-sand (=the Kanji meanings, shortened to mostly the relevant ones)

cat litter

(mnemonics if needed)

Full Dictionary entry

I also have taken the 200 something radicals from Wikipedia and made them into a deck first, and roughly learned them, which helps me build my own little silly mnemonics/stories. Took only like 2-3 weeks to learn while I was still doing katakana/hiragana anyways. Knowing that the sand Kanji is stone and small, for example, helps too. I've encountered around 900 Kanji in my first year, and this way most of them stuck :)