HP: Route 1
You can easily defeat Azurill/Marill for a bunch of HP fast.
(Edit: You could also use the assorted Chansey next to the Fairy Team Star base to grind easy)
HP: Glaseado Mountain
Hariyama line, Dunsparce, Driflim line, Chansey, Clodsire line, and the Greedent line are more efficient than above, but its a little later.
Attack: North Province (Area 2)
Bisharp, Pawniard, Scyther, Lokix, Teddiursa, Ursaring, and Heracross are all easy to KO and get Attack.
Defense: Asado Desert
Orthworm, Hippopotas, Hippowdon, Silicobra, and Sandaconda are the ones you will be looking for.
Special Attack: The Great Crater of Paldea
Glimmet and Glimmora may be the only non-version-exclusive easy to get Pokemon in Area Zero, but the sheer amount of them will get you there in no time.
Special Attack: Timeless Woods
Less mind-numbing than Area Zero. Hatterene line, Gardevoir line, and the Chandelure are slow and easy to KO.
Special Defense: Tagtree Thicket
Flabebe, Toedscool, Goomy, Hatenna, Hatremm, Swablu, and Altaria will get you to the AV Garchomp of your dreams.
Speed: The Great Crater of Paldea
Dreepy, Dragapult, Espathra, Iron Bundle, Talonflame, Raichu, Meditite, and Medicham are the ones you are looking for.
good enough its like 3 am