Making mnemonics for every word takes too much time. Recalling the mnemonics also takes additional time. In addition, you want to have a short connection between a word and its meaning in your head. A mnemonic would just stay in the way.
It may be hard to remember new words in the beginning. If you can't remember a card after a few tries, let Mortician bury it for you. Bury or suspend difficult cards to learn more easier cards.