Writing the finale first ensures that you always have a lifeline and that, if you go lost, you can easily find your way back. Keep in mind that readers enjoy traveling. They are fascinated by beginnings, middles, and endings. It might serve as a checklist of the information you wish to convey in the finale. Also, it's easier to surprise your reader with a twist at the end than it is to keep them guessing throughout the story.
One of the key reasons why writing the conclusion first is such a good idea is because after you've written it, you can work on it and edit it throughout the rest of the book's existence. This signifies that your finale is being tweaked and perfected for the longest duration of any portion of the book. Opening with the ending ensures this.
It also prevents you from getting stuck in a story-telling rut. By starting with the ending, you are encouraging yourself and your audience to think about what will happen next. There are no right or wrong answers as long as they make sense within the narrative framework of the book/movie/series.
The opening scene of Harry Potter and the Deathly Hallows - Part 1 is exactly this: J.K. Rowling has Potter himself wonder when he should begin his story since it isn't really possible to go back in time. She responds by saying "anytime". This allows Potter to begin his tale at any point over the last 10 years and still have it make sense within the narrative flow of the series.
This technique is used quite often in fiction writing courses where students are asked to write scenes that open up their stories in some way. The goal is that by showing not telling, writers can avoid boring their readers who want to know how characters are doing next chapter but instead are given the opportunity to connect with them on an emotional level through observation rather than explanation.
Your conclusion must wrap up any loose ends and provide answers to any unresolved issues in the tale. Writing the conclusion is just as vital as writing the introduction. As a result, you must create an ending that sticks with the reader. The conclusion must also be a logical conclusion to the tale. It cannot leave your audience wondering what happened to their characters.
In general, a short story conclusion can be as simple or as complicated as you like. Sometimes, it's enough to simply state what has occurred in the past few scenes and let the reader imagine the rest. But if you want to go out of your way to leave your readers guessing about what will happen next, you can always throw in a surprise twist at the end of your story. This could be something as simple as switching which character we are focusing on (the protagonist might not even appear in the climax), or it could be more complex than that. But no matter how you choose to end your story, just make sure you don't leave your readers feeling cheated.
Here are some examples of short story conclusions: "The boy found his father lying in the grass. He was bleeding badly from a head wound. The boy knew immediately that his father was dead. He cried for several hours before finally falling asleep." - This story doesn't have a clear-cut climax. We know that the main character finds his father at the beginning of the story and then wakes up to discover that he is dead.