In “What is Flash Fiction,” the  writer and teacher Katey Schultz offers this definition of the Flash Fiction form. Schutlz identifies five components that in her mind characterize the form. Tips 1-3 are helpful for understanding the definition of what flash fiction is.
Tips 4 and 5 are helpful for composing flash fiction (as you are now doing):
4. Flash fiction employs lyrical writing, which means that every word bears weight and bends the right direction. In lyrical writing, the skeleton of the sentence perfectly enhances its content and vice versa. It also means that flash avoids high-speed chases for the sake of themselves, for instance, but can certainly include high-speed chases for the sake of yearning, of revealing, of epiphany. –Katey Shultz
5. Flash fiction is the story of smart surprise. It is always leaning toward “explosive moments of tremendous clarity” (Baxter, again). It catches us unaware by showing us that what we were looking for was always already there. In short—the truth is under our noses and flash enables us to see it.-Katey Schulz
https://fictionsoutheast.com/what-is-flash-fiction/
In the post below, Katey Schultz discusses the “five s’s” of flash fiction in a video.