Sharing your raid Online, and keeping it indefinitely

1. Play the game right before midnight (on the Switch. This is a recurring pattern, so I won't explain this every time)
2. Save the game before midnight
3. Close the game before midnight
4. Wait for midnight to hit
5. Perform a date or time change (exact date doesn't matter, what matters is a change away from the Switch's date happened).
This triggers the Switch to be in a date changed mode.
6. Now launch the game, and the frame is there

Alternatively, if you don't play the game right up to midnight, and you're unsure
1. Always perform a date change before you launch the game. (game has to be closed during this)

1. You are the host, hosting online the shiny raid for your friends.
2. Let the raid begin. Let it show at least the knees of your character/participants
3. Hold down on the HOME button on the Switch
4. Activate Flight Mode. If you were already in Flight Mode (with Wifi on), turn off Wifi
5. This should kick you (the host) back to overworld, with den still active with that species.

This method does not work for hosting locally.

1. Do not save when the den you rolled has the wanted species on the shiny frame
2. Host the raid online, then close the game
3. Use ^ + B + X  on the title screen to restore to the previous save
4. You'll see the hosted raid was of the wanted species, and it was on the shiny frame.
5. Do not save here
6. Now rehost it for your friends
7. Once they catch it, play normally through the title screen (no need to restore previous save).
If your last save point was 3 frames before the shiny, you'll load up there.

Explanation:
So what happens here is the game does something weird. Even with auto save off, the game apparently saves right before a raid you hosted, and that save is specifically only into the backup save, even if you didn't save in-game.

Normally, if you load the game normally at the title screen, you will not encounter this oddity.
However, this can be used to host old raids, while keeping >3 shiny frames away on your main save.

If this explanation didn't make sense, think of it as this:
3 frames away from shiny - designated as "past"
hosting a shiny raid - designated as "future"

Whenever you host a raid, the game stores your "future" as a backup save, while the "past" is still your main save.
Normally when you save in-game, it duplicates the save into main and backup.
However, for this instance, you have two different saves in main and backup.
Thus you can always go back to the "future", if some situation requires it.

Note: just a reminder, this only works for any raid that was shared successfully online.
I usually share online twice to be sure. Sharing locally doesn't fit this criteria FYI.