Mary Shelley's original title for Frankenstein was Frankenstein, or the Modern Prometheus; Prometheus was the Titan god who was entrusted with the task of molding man out of clay. Added to this concept of creation from matter, Mrs. Shelley and her husband both were intrigued with the ideas of Eramus Darwin, a scientist whose ideas concerning biological evolution prefigured those of his more famous grandson, Charles Darwin. Also, Mary and Percy Shelley attended a lecture by Andrew Crosse, a British scientist whose experiments with electricity greatly interested them.
With these influences in mind, as well as the historical context of the novel, it seems more appropriate to believe that Frankenstein molded his creature and charged him with electricity than having created him in a test tube. After all, Dolly the sheep was "created" much later than Shelley's time. In fact, in the novel itself, Victor relates how he used cadavers' flesh and bones to create his creature:
I collected bones from charnel-houses; ....The dissecting room and the slaughterhouse furnished many of my materials....
Frankenstein's more "filthy creation" as himself calls it serves Shelley's gothic theme, as well as the Romantics antipathy for science.