I found this sentence in a fiction I'm reading and am confused about what したて means after 弟子入り. Context: He is talking to a young merchant who reminded him of himself when he was younger.
なんだか、親戚の行商人の元に弟子入りしたての頃を思い出したのだった。
Although I understand the gist of the sentence, I've never seen したて as a form of する. I thought maybe it might be 仕立て from 仕立てる to meaning training? So 弟子入り仕立て would mean something along the lines of "Apprentice in training"? Is this correct or am I interpreting it wrong?