Genocide route (Tyranitar) @ Chople Berry  
Ability: Sand Stream  
EVs: 160 HP / 88 Atk / 16 SpA / 244 Spe  
Lonely Nature  
- Crunch  
- Pursuit  
- Superpower  
- Fire Blast  

Friend Pellets (Ferrothorn) @ Leftovers  
Ability: Iron Barbs  
EVs: 252 HP / 48 Def / 208 SpD  
Sassy Nature  
IVs: 0 Spe  
- Spikes  
- Gyro Ball  
- Knock Off  
- Leech Seed  

True Heroine (Mamoswine) (F) @ Leftovers  
Ability: Thick Fat  
EVs: 252 Atk / 4 Def / 252 Spe  
Jolly Nature  
- Substitute  
- Earthquake  
- Icicle Crash  
- Ice Shard  

Happstablook (Rotom-Wash) @ Leftovers  
Ability: Levitate  
EVs: 248 HP / 20 Def / 240 SpD  
Calm Nature  
IVs: 0 Atk / 14 Spe  
- Will-O-Wisp  
- Hydro Pump  
- Volt Switch  
- Pain Split  

!Core (Heatran) @ Leftovers  
Ability: Flash Fire  
EVs: 248 HP / 140 SpD / 120 Spe  
Calm Nature  
IVs: 0 Atk  
- Protect  
- Stealth Rock  
- Lava Plume  
- Earth Power  

Birds are singing (Latios) (M) @ Choice Scarf  
Ability: Levitate  
EVs: 252 SpA / 4 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Draco Meteor  
- Dragon Pulse  
- Surf  
- Trick  

This is a very interesting and fun sand team that I builded for my game versus Finchinator, in the Past Gens Championship 2020 tour.

Tyranitar have a diferent spread than the standart slow support because its function here, alongside Pursuit trap Psychic-types, is to open holes versus common defensive cores and even pick some surprise KOs because of it Speed, that outspeed Modest Magnezone. Since this team didn't have a Rapid Spin user, Fire Blast is the prefered coverage option to nuke away Ferrothorn and Skarmory before they can Spikes stack.

Ferrothorn is the standart set with Leech Seed to help its teammates, especially Heatran and Tyranitar. Knock Off and Spikes are awesome to pave a late game sweep with Mamoswine or Scarf latios while Gyro Ball let it have a way to damage Breloom and Dragon-types that tries to use ferrothorn as a setup fodder.

Mamoswine is the team star, since all of the support it receives makes it deadly dangerus. Leftovers may apear a bit odd but this let it outstall Rotom-W Hydro Pump since Rotom-W need to hit a minimum of 5 in a row to defeat it, and Ice Shard alongside a Scarf Latios makes this team very strong versus Hyper Offense structures.

Rotom-W here is to make sure the team have options to counter rain and, at the same time, to give some nice defensive utility versus Excadrill or Garchomp sand teams. Will-O-Wisp support all of its teammates no matter who Rotom-W burn so its a very spammable move. Not much to add here, Rotom-W is pretty straightforoard and intuitive to use.

Heatran here adds another Psychic-types check and is the ideal Stealth Rock user for the team. It's also another Pokemon that pressures Spikes users, so this is a bonus. Lava Plume should be spammed after Rocks are up to fish for burn. Earth Power is mostly to hit mirror Heatrans, so it didn't lose momentum, and to pressures Tentacruel alongside dealing damage to Tyranitar and Terrakion, that could try to hard switch into it. Its Speed is for Modest Magnezone and slower SpDef Excadrill.

Finally, Scarf Latios glues the team together. As said before, it is one of the best HO answers in the meta, especially versus DragMag structures. It also soften the rain MU by checking Thundurus-T and by Tricking Ferrothorn or Jirachi a Choice Scarf.