The book doesn't specify if the monster was created by one man or several or how he was brought to life. I think we can safely guess that the monster was brought to life using electricity because it has such an influence on Victor. SPOILER ALERT. I would also say that is safe to say that the monster was probably created using more than one man because later on Victor tears apart/destroys the monster's companion before he completes her creation. These are just my thoughts and if anyone has anything else they would like to add please comment
At the age of thirteen, while on a visit to picturesque French spa town of Thonon , Frankenstein happened upon a work by Cornelius Agrippa. Although his father dicouraged him Frankenstein continued to read his works and those of other alchemists, such as Paracelsus and Albertus Magnus . When Frankenstein was fifteen years old a storm struck an old oak just twenty yards from their home. A researcher of natural philosophy who was present at the time explained how the event related to his own theory of electricity and galvanism, Frankenstein attributes this man's explanation to his rejection of the alchemists who he had previously read, saying "he [...] threw greatly into the shade Cornelius Agrippa, Albertus Magnus, and Paracelsus".