In Slateport City, there's a hyper rank contest place. Inside, talk to the little girl and she'll give it to you.
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In Pokemon Ruby,Sapphire and Emerald after you make a pokeblock, you can check the pokeblock case and you give the desired Pokemon the pokeblock to help it do better in Pokemon contests. After you have received a pokeblock case and you made pokeblock at the berry blending machine go to your key items in your bag and scroll down to your pokeblock case then simply select the pokeblock you want to give your Pokemon.
in what Pokemon? in Pokemon ruby/sapphire and maybe emerald too, a girl in slateport contest house give it to you
This depends on the pokemon's nature, not the species.
The pokeblock case in Pokemon Quartz is located in Seablue City. Seablue City can be found in the Safari Zone.
Mix one out of berries. It will be in your pokeblock case. Feed it to the Pokemon that you want to give the pokeblock to.