A familiar pure stall loop team. To counter the new Mega Mawile, which is difficult to wall due to its wide offensive power and move pool, I started building around Mega Meganium, which has Mega Solar Synthesis recovery and a guaranteed one-hit KO with Weather Ball. After completing the core with a general physical wall Slowbro and a general special wall and draw-prevention Snorlax, I added Toxapex with Haze to deal with Mimikyu, Ceruledge, and physical Aegislash holding Punching Glove-like items, which these three couldn't wall. Finally, I added a Scarf Hisuian Samurott to outspeed and deal with Delphox, Gengar, and Gholdengo, and inflict cumulative damage to the backline, patching up the stall's weaknesses.
Toxapex (Opal Berry, HB): Traps opponents with Infestation + Toxic, and resets stat boosts with Haze. While Mimikyu with Swords Dance has become difficult to wall since the introduction of Punching Glove-like items, Toxapex is still strong in a direct confrontation.
Mega Meganium (Meganiumite, Mega Solar): After Mega Evolution, its actual stats are 187-100-170-163-135-114. It's a dedicated counter that endures Mega Mawile's Play Rough with Synthesis recovery, withstands Swords Dance-boosted Fire Fang, and then retaliates with Weather Ball. It was also strong against Taunt Gyarados, Hisuian Samurott, and Corviknight.
Slowbro (Slowbronite, Shell Armor): After Mega Evolution, its actual stats are 201-85-255-152-101-50. It's a versatile wall that can take most physical Mega attacks, using Scald to aim for burns and a Body Press + Iron Defense combination.
Snorlax (Leftovers): A versatile special wall with Earthquake and Float-like moves, also serving as draw prevention. Against high-power special attackers like Hydreigon and Mega Dragonite, it had limited HP, so it was operated in conjunction with Toxapex's Toxic.
Hisuian Samurott (Choice Scarf)
Against the Hydreigon + Metagross combination, I led with Toxapex, Slowbro, and Snorlax. Against Mawile, I added Meganium. Against Delphox, Gholdengo, and Mega Gengar, I centered my strategy around Hisuian Samurott.
The combination of Mawile + Delphox + Mimikyu, Swords Dance Outrage Mega Charizard X, Mega Florges, and Swords Dance Poltergeist Aegislash holding Cursed Body were particularly troublesome.