Ahh... Carbink. AKA Shuckle Lite. Their stat distributions are fairly similar. Polished Defenses, Lackluster everything else. However the disparity between stats is not as great as Shuckle's, making Carbink slightly frailer in return for better offenses (still badly cut) and a slightly better HP stat. Rock Fairy does Carbink far more favors than Shuckle's Rock/Bug but it doesn't change the fact that Carbink is an extremely passive Pokémon.
Rose's Shield
Carbink
Ability: Sturdy
Item: Light Clay
-Reflect
-Light Screen
-Stealth Rock
-Gravity/Magic Coat/Toxic
Nature: Bold (-ATK, +DEF)
EVs: 252 HP/252 DEF/4 SDEF
Yeah, couldn't avoid the SU reference. Anyways, dual screens Carbink. Set up Reflect and Light Screen, Stealth Rock if you have the time and GTHO (get the heck out of there). Last move is up to preference. Gravity is a great support moves that makes attacks more accurate and grounds many pokémon, making them vulnerable to Earthquake. Magic Coat bounces status moves back to the opponent like Entry Hazards, Taunt, Toxic, and Defog. Toxic is a way for Carbink to actually have an offensive presence.
EVs are for a more physical leaning, since if a Sandstorm is thrown up, Carbink's natural SDEF becomes rather impressive. That being said, that is only a possibility and it is perfectly fine to mix and match DEF and SDEF EVs. Nature should be attack reducing to reduce confusion and Foul Play damage (if you aren't running any physical attacks).
Counters and Checks
Carbink is very passive Pokémon, one that many pokémon can use to setup (hazard setters need to beware of Magic Coat though) without fear of retaliation beyond Carbink setting up in turn. Steel Types like Alolan Dugtrio, Mawile, and Alolan Sandslash are particularly bad for Carbink, immune/resist to the vast majority of its offense and able to OHKO/2HKO it with 4x effective STAB. The more pressing matter is preventing Carbink from supporting its teammates. Stealth Rock, Trick Room, Reflect and Light Screen can be game changers if thrown up. Defog attends to most of these and Taunt stops Carbink cold, but both moves can be reflected with Magic Guard. OHKOing is near impossible thanks to Sturdy, but Mold Breakers (Rampardos, Pinsir) and Pokémon with multihit moves (Marowak) can oneshot Carbink before it can setup.