[Overview]
In a metagame with a large amount of fighting types, Slakoth's typing alone puts it in a disadvantage. To compound Slakoth's problems, it has what can be considered the worst ability in the game in Truant and average stats at best. Using this Pokemon requires large team support, and it's very rarely even worth it. It lacks the speed to really utilize a Choice Scarf, and low defenses and HP, along with Truant, make using an Eviolite a lost cause. It can't even use Trick Room effectively, as Truant uses up half of the precious turns. This sloth hasn't learned any new tricks since the last generation, which shows if you try to use this Pokemon.
[SET]
name: Choice Band
move 1: Return
move 2: Ice Punch
move 3: Hammer Arm
move 4: Pursuit/Sucker Punch
item: Choice Band
ability: Truant
nature: Amanant
evs: 196 Atk / 40 Def / 236 SpD / 36 Spe
[SET COMMENTS]
This is the only set Slakoth can really run to any good effect. Return is the STAB move of choice, with 102 Base Power before STAB or the Choice Band is even calculated. Ice Punch is used to hit Dragon- and Ground-types super effectively, and Hammer Arm doing the same to Normal- and Dark-types. The final moves is a matter of preference, Pursuit being used to high Ghost- and Psychic-types super effectively, while Sucker Punch can be used to help with Slakoth's bad speed.
[ADDITIONAL COMMENTS]
The Evs are chosen to maximize Slakoth's attack, and serve to equalize Slakoth's defenses to a lackluster 22/13/13. The 36 Speed EVs put Slakoth at 10 Speed, outspeeding slower walls such as Bronzong. Adamant nature is used to boost Slakoth's Attack even more, putting it at 16. No other nature should be used, as Slakoth doesn't need Special Attack on this set and Attack is the main stat to be boosted. Choice Band is chosen over Life Orb due to the fact that Slakoth can't afford to spare HP, and Slakoth isn't likely going to survive long enough to need to change moves regardless, unless you switch.
Good teammates for Slakoth are Pokemon who are capable of switching in to an attack, sometimes repeatedly, and being able to shake it off. Bronzor and Lileep are two examples of this, and are exceptional due to being immune to certain types, such as Poison, and with Levitate, Ground for Bronzor, and Lileep can switch in on a Water-type move, use Storm Drain to raise it's Special Attack, and OHKO with Giga Drain. Misdreavus, being immune to three types, can find an ample amount of opportunities to switch in for free, and Mienfoo can switch in on most non-super effective moves, Fake Out, and then U-turn away, healing with Regenerator.
[Other Options]
Aside from the above set, Slakoth doesn't have a lot of options. It can use Swagger, but doesn't have the defenses to survive a +2 hit from many Pokemon. It learns Substitute, but it's unlikely to last long enough to be of much use. Slack Off provides healing, but he likely won't live long enough to use it.
[Checks and Counters]
Anything with Protect can counter Slakoth and do whatever they want on the Truant/switch turn, be it set up, switch out themselves, or put Slakoth out of its misery. Anything faster than Slakoth that can OHKO it also serves as a counter.