The tense in the flashback would need to be consistent with accordant timing.
I’m not sure it’s necessary to use a sentence containing the past perfect tense and then go into a lot of detail; it may be more effective if you just start the flashback in whatever tense you choose to use in a new paragraph.
Similar questions in English
Asked by Abdulrahman
Describe mechanical digestion using one example?
Asked by Kymbyr
What is literary analysis?
Asked by Selina