Meaning of したて after a する-verb


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?

