NFE PhysDef Spikes (Shelmet) @ Eviolite
Ability: Overcoat
EVs: 248 HP / 252 Def / 8 SpD
Bold Nature  
IVs: 0 Atk  
- Spikes
- Recover
- Yawn
- Bug Buzz
Optional Move(s): 
- Infestation
- Toxic
- Toxic Spikes
Optional Item(s): 
- N/A
Optional Ability: 
- N/A
Optional EV/IV(s): 
- 248 HP / 8 Def / 252 SpD (Calm)
Overview: Thanks to its solid bulk and access to reliable recovery, Shelmet makes for a solid Spike setter, which can check physical threats like Machoke, Alolan Grimer, and Metang. However, Shelmet is very passive and relies heavily on Yawn to not be setup bait. It faces stiff competition from Spikers which outclass it, such as Roselia and Quilladin, and is only really used on semi-stall, which is a niche playstyle. 
PhysDef Spikes: Shelmet's amazing physical bulk allows it to set up Spikes freely against most physical attackers and lets it serve as a solid check to the best physical wallbreaker in the tier, Machoke. Recover lets it switch in multiple times, giving it more opportunities to set Spikes up. Yawn synergizes well with Spikes as it forces switches and helps to accumulate passive chip damage. It also helps with Shelmet's passive nature, making it harder for opposing Pokemon to set up on it. Bug Buzz is a good STAB move that deals decent damage and lets Shelmet chip opposing Pokemon for its teammates.
Checks and Counters: Shelmet is extremely passive and lets setup sweepers, such as Clefairy, Monferno, Pawniard, and Fraxure, switch in freely if the opponent already has a Pokemon which is asleep. Defog users, such as Staravia and Vullaby, can easily switch into Shelmet, and either remove the Spikes or threaten it out with their super effective STAB moves, although they dislike switching into a status move. Specially defensive Servine does not take much damage from Bug Buzz and is able to set up on and lure Shelmet with Hidden Power Fire or Defog away Spikes. However, it does have to be careful of Toxic. Shelmet's weakness to Stealth Rock can limit its ability to reliably switch into bulky Pokemon such as Marshtomp, Metang, and Togetic, which do not take much damage from its attacks and can wear it down with Toxic. 
Optional EV/IV(s): An alternative spread of 248 HP / 8 Def / 252 SpD with a Calm nature turns Shelmet into a specially defensive wall instead, letting it better switch into special attackers such as Servine, Electabuzz, Frogadier, and Kadabra, at the cost of being a less reliable check to physical attackers.