Well in Azaelea
You can catch Slowpoke in Pokemon Gold in the Slowpoke Well that is by Azalea Town and you can also find them in Tohjo Falls.
You can get it at Slowpoke Well, or Celadon Department Store
Slowpoke is only available in leafgreen.
You can find slowpoke near Azalea town.
You find the kings rock in the very bottom of the Slowpoke Well (Near the town with the bug Pokemon gym)
You can find slowpoke in pokemon white if you go to the Abundant Shrine, and use surf on the water. When you see a ripple in the water, go to it. Sometimes the wild pokemon is a slowpoke. I have caught one before like this, it works.
leaf green only.
You can catch Pokemon 14 which is Slowpoke in Kisara Plains, where you catch two Abra and then Slowpoke will appear near the guy in the Kisara Plains.
Usually you can find it in seafoam islands.
you can get slowpoke in pokemon td in 5.6
in Pokemon platinum, you can find slowpoke in the north side of route 205. But, you need to use a pokeradar to find or else its not possible. hope i helped :)
To catch a slowpoke you have to catch 2 Abra then a slowpoke will appear. It's attack is a yawn cloud. PS: Do this at the Grassland capture challenge