Requirements:

• The Isle of Armor expansion pass
• 10 Armorite Ore

If you have the expansion pass, you can go to the Workout Sea in the Isle of Armor and there's a small island with an NPC who will reset a Pokémon's EVs for 10 Armorite Ore.

Directions:

From the Dojo, go straight across the bridge, hang left around the rock into the Workout Sea, keep a slight left heading to the first small island near the cliff.