Update 2: Following the delay mentioned below, the distribution of the Galarica Wreath – an item necessary to evolve a Galarian Slowpoke into a Galarian Slowking – is now live in Pokémon Sword and Shield for a very limited time. You can get the item by entering code CR0WNF1NALS on the Mystery Gift screen in-game.
The code will only remain valid until 2:59pm UTC tomorrow, Sunday 7th February (thanks, Serebii). That's 6:59am PT / 9:59am ET / 3:59pm CET.
Update 1: Sadly, Serebii reports that the Tournament Finals during which the special code was planned to be distributed has been delayed, meaning that it may be a little while before you can get your hands on the free Galarica Wreath:
Original Article (Fri 11th Dec, 2020 14:30 GMT): Next week, Pokémon Sword and Shield players will be able to easily get their hands on one of the game's more awkward-to-obtain items.
During the South Korean Pokémon Sword and Shield Crown Tournament, which is set to be livestreamed online, a distribution code will be released which grants players one Galarica Wreath. This special item is the only way to evolve a Galarian Slowpoke into a Galarian Slowking, so collectors and Pokédex completionists will want to grab it while they can.
Serebii reports that the code will "run for just 24 hours from the start of the event to 14:59 UTC December 20th." Codes aren't region-locked, so you'll be able to get the Galarica Wreath no matter where you're based once the code is shared.
It's worth pointing out that you can get a Galarica Wreath in-game without using a special code, but it's one of the more time-consuming items to obtain. To get one, you'll need to find no less than 15 Galarica Twigs – an already relatively rare item itself – and hand them over to an NPC in The Crown Tundra's Roaring-Sea Caves. If you're struggling to find them, this will be a great opportunity to speed up the process.