Here's how to get it in Black 2:
* Route 10 (Black City): After obtaining the National Dex, you can find an Oval Stone by searching the tall grass along Route 10.
The Oval Stone is a rare item, so it might take some time to find it. You can increase your chances of finding it by using the following tips:
* Use the Poké Radar: The Poké Radar can help you find hidden items, including the Oval Stone.
* Search the tall grass: The Oval Stone is found in the tall grass along Route 10.
* Be patient: It may take several attempts to find the Oval Stone.
The Oval Stone allows Pokémon to learn their Hidden Moves. It's a useful item for those who want to complete their Pokédex or train their Pokémon to their full potential.