Yeah, that's what I'd say in English, too. "I build models."
In Japanese, I'd say "puramo wo tsukurimasu" (I build plastic models) or "mokei wo tsukurimasu" (I build models), or just "mokei zukuri" (model-making) if asked what my hobby is.
None of these phrases, by the way, would be mistaken for the other type of modeling!