There are a few catches to consider here, though - firstly, you'll need at least one Divine Beast dungeon unlocked but undefeated, and you'll also need to have purchased the aforementioned DLC.
If you fulfil both of those base requirements, then this is how you get unlimited Korok seeds:
Go to the Trial of the Sword location in the Lost Woods and enter, then teleport to any unlocked but unbeaten Divine Beast dungeon.
Exit the Divine Beast - you can teleport out if you don’t have the Beast's map or press X to exit if you do.
Visit a Shrine to confirm the glitch has worked - if it has, the shrine entry pad will be orange, even if you’ve beaten it.
Find a Korok Seed you haven’t collected yet. Place down the Travel Medallion (which is part of the Trial of the Sword DLC - check out this guide if you haven't found it yet) and then pick up the Korok Seed.
Travel back to the area using the Travel Medallion and you'll find that the Korok has returned. Pick it up again, and then repeat as many times as you wish.
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This glitch doesn't just let you collect unlimited Korok seeds, however - it can also be used to obtain multiple copies of the same item, such special DLC armour, Champion weapons, Hestu's Maracas so on.
If you fulfil both of those base requirements, then this is how you get unlimited Korok seeds:
Go to the Trial of the Sword location in the Lost Woods and enter, then teleport to any unlocked but unbeaten Divine Beast dungeon.
Exit the Divine Beast - you can teleport out if you don’t have the Beast's map or press X to exit if you do.
Visit a Shrine to confirm the glitch has worked - if it has, the shrine entry pad will be orange, even if you’ve beaten it.
Find a Korok Seed you haven’t collected yet. Place down the Travel Medallion (which is part of the Trial of the Sword DLC - check out this guide if you haven't found it yet) and then pick up the Korok Seed.
Travel back to the area using the Travel Medallion and you'll find that the Korok has returned. Pick it up again, and then repeat as many times as you wish.
************
This glitch doesn't just let you collect unlimited Korok seeds, however - it can also be used to obtain multiple copies of the same item, such special DLC armour, Champion weapons, Hestu's Maracas so on.