I am a new-ish author. I've written a lot of books, but they've never been published. Anyway, for this new book I'm about to write the first scene is a flash-forward to the end of the book. I really want to write the rest of the book in present tense, is there a way I can write that flash-forward scene so it is in the future and the rest of my book is present? Also what would be a good transition from future to present? Because "let me start from the beginning" is so movie-like.
Sometimes What Works in a Movie Works in a Book
If you have a chatty narrator, having her/him say "let's go back to the beginning" or "but I'm getting ahead of myself" or anything that indicates the time shift is totally fine.
You can also put it into the chapter headers.
"Many years ago..."
Or you can indicate it by referencing a character's age. For example, if the prologue (your fast forward opener) shows the character surrounded by grandchildren, maybe your first chapter (the first one in the predominant time) references the character graduating from college. Or if the prologue shows a character getting married, maybe the first chapter shows the character in kindergarten.
Note that you don't have to separate out future and present into different chapters, but you will have to make them distinct in some way, even if it's through the narrator.
You do need some sort of external reference like my examples, because changing the tense of the chapter will not convey enough information.
In a movie you can use the setting to convey a large time shift backwards and do a fade from a character's face to a younger version of the same actor or a different one (in which case the first line after the switch is usually includes the character's name). In a book you will need to be more explicit (as movies often are as well).
What's important is that the reader understands what you're doing. How you accomplish that is up to you.
The story's tense is all about your narrative voice. It can't orient the reader to a larger timeline structure because no matter what tense is used the reader's now is where they are reading.
The narrator and reader exist in the reader's present. The narrator can use tense to indicate events in the narrator's past, or the narrator's future, but the communication between narrator and reader is always "right now". When the narrator changes tense, it is relative to the narrator. If the narrator starts talking in future tense, it's a prophesy. The reader does not feel as if they are in the future.
On the flipside, if the reader skips ahead by a chapter she is not experiencing the book "in the future". She is still reading the book "right now". The reader doesn't experience time the way the narrator does. That's how the narrative voice stays in one tense through an entire novel. The reader is always "right now" and the narrator gives in-story clues to let the reader know how much time has passed since the last scene.
You should stick with the tense of your narrative voice, and begin in medias res. Then consider when and how to transition the story back to an earlier event, indicated through in-story clues. Let the reader do a little detective work on their own and they will become more involved by the process.