How were the Three and the rest made?

[Knight of Gondor]

I believe it was in one of the Histories of Middle-Earth that Tolkien wrote about how the art of ring-making was studied deeply by Saruman, in hopes that he too could one day obtain the ability to craft rings of power. (First mentioned in Fellowship; Saruman was wearing a ring when he met Gandalf, and Elrond lamented that it was perilous to study too deeply into the arts of the enemy.)

I think it was also written that if Saruman had been left alone, he might possibly have attained that level of knowledge, though probably not to the level of power that Sauron or even Celebrimbor.