My procedure starts with filling the top-left box, not the top row. So it looks something like this after the third step: 12.. 34.1 .1.x ..1. From her

My procedure starts with filling the top-left box, not the top row. So it looks something like this after the third step: 12.. 34.1 .1.x ..1. From here x can be any of [2,3,4], and each yields exactly one solution!