Where to Find and Catch Slowking
From Pokemon Go Wiki
Slowking are found and captured in Nest and Habitat locations.
Nests
Slowking Nests are locations that consistently spawn Slowking.
Habitats
Slowking Habitats are spawn locations where Slowking is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: