This isn't intended as a thorough guide to getting a shiny den. If you're looking for an extensive guide, consider using the one by /r/PokemonMaxRaids which is available here.
A hacked switch is NOT required to use this guide.
If you're just looking for the seed checker (シードチェック): https://cute.berichan.net/
- Make sure you have autosave turned off in settings, if you don't then you will lose your den as soon as you finish it.
- Put a wishing piece in the den you want shinies from. Use https://www.pokeatlas.com/ to take a look at what each den contains (Isle of armor can be toggled from the top bar)
- Make sure you have the correct den (rare: purple thick beam, common: thin pink beam) for the pool of pokemon that you want.
It's vital that you DO NOT save throughout this entire process.
- Go into your den (either online or offline, up to you), defeat and catch the pokemon in it.
- Go to https://cute.berichan.net/ and do your best to trade the bot. When you get in a trade with it, put up the pokemon you got from your den. Note: The bot won't trade anything back, it'll just cancel the trade once it has the information to get your seed.
- After 5-10 seconds, the page will show you your seed. If for any reason you missed it, you can view the last 20 seeds on the page or by clicking here The bot should also tell you how many days away your closest seed is. You can use a program like RaidFinder or SeedChecker to get a detailed breakdown of your closest shiny frames too. If you feel like your shiny frame is too far out, remove the pokemon from the den by fainting/catching it and put a new wishing piece in. Anything below 1000 is great.
- Restart your game, your den should have the pokemon back in it as long as you did not save.
- After you've picked the frame you want to jump to, you need to start skipping days. You want to save on the day exactly 3 (not including the shiny frame day) before your shiny frame.
- You can use something like a date calculator to check your shiny date. Remember to pick 3 (or around 5-10 to be safe) days before the frame count.
- Start or complete an online battle (link battle is fine). You can exit at any time from the starting connected screen but don't annoy people actually looking for battles, try to do this with a friend.
- Test: take the watts out of your den. Then, while the game is open press Home > System Settings > System > Date and Time. Skip one day forward and go back into the game. If the test worked then your den will have watts again and one day will have passed. If not, go to step 1.
- If all is well, go to somewhere like a pokemon center and save with the pokemon still in the den and start skipping days. I find that placing your switch on a semi-raised surface and skipping days using the touchscreen is the fastest method. There's no reason to go back into game, but after every 90 or so days you should do a rotom lottery and save just to make sure you are skipping successfully (the rotom lottery will fail if you're not) If at any point you close the game, you'll need to go to step 1 and start over.
- Once you're at what you think is the 3-day-before point, save the game. Do not save the game if you think you've gone too far and recheck your seed instead from your last save.
- You can check the frame you're on by catching the pokemon in the den (without saving!) and use the bot to get the seed for that frame. Alternatively, use RaidFinder or SeedChecker, plug in the den and pokemon species you've caught and check that the IVs/Nature/Gender/Ability match up with the frame you think you're at. Restart the game to get the pokemon back in the den with your beam still up. If you're still not at the 3-day-before date, skip days until you are, checking whenever you think you're close.
Once you're at the 3-day-before date, you should "roll" the pokemon in the den by skipping 3 days using this method.
- Disconnect from the y-comm.
- Start up your potential shiny raid and search for participants (no one should join as you're not online)
- Once the raid timer starts counting down, do what you did before and change your system date (Home > System Settings > System > Date and Time) by one day only.
- Go back into the game, press B a few times, collect watts if day skip was succesful. Go back to 2 and repeat. Go to the next step once you've completed this process 3 times.
- Go into your den, your shiny pokemon should now be there! If you didn't get the species you wanted, just close the game and start from 2 again to reroll your shiny frame. Don't save from this point on until/unless you want to lose the shiny den. If you accidentally go one day forward, close the game and set your switch clock one day back. This won't work if you've saved, though.
You can host online as normal. Just hit airplane mode once the raid starts to disconnect yourself (once you see your legs in the opening animation) and your participants will continue the raid as normal, but your moves will be selected by the AI. You can host the same raid again for others while doing this.