I put aphantasia into forum search and found a bunch of topics discussing this. Hopefully any of these can help. I only picked the top results so there might be more full on topics about it. Hopefully one of these have some tips that might work for you. 
Having aphantasia means âimaginingâ doesnât work
Mnemonics and aphantasia (lack of a mindâs eye)
Do people with Aphantasia have a hard time learning with mnemonics?