Thank you very much, Julie-san; I really appreciate your helpful explanation.
The good folks on here have been trying to educate on explanatory の usage for some time now...I guess I'm a slow learner.
The dialogue I was referring to was from the Minna textbook...I have been going back to some (ancillary) material in earlier chapters that I hadn't reviewed yet. The chapter that this dialogue came from is earlier than the Minna chapter that discusses the explanatory の concept.
I know it's an artificial form of analysis but I thought to myself that the textbook authors were trying to express a construction that had already been studied rather than a concept from a future chapter.
Interestingly, later on in the dialogue, (and I was listening to this after I had posted my original question here), another speaker says (referring to a Mexican hat): 「お祭りの時、男の人が被る帽子だよ。」 I think this was the sentence pattern that I had in mind when I heard 「私が作ったの。」 The sentences seemed similar to me.
A few weeks ago, Toritoribe-sama was explaining to me an example of の as a pronoun using this sentence: 「 そこにある
のを貸してください。」 In this sentence, の was a pronoun that was replacing a noun understood in context, the sentence would otherwise have been 「 そこにある
本を貸してください。」 So I thought this seemed applicable.
With the explanatory の explanation, I'm still not quite sure why が would be used. 私が作った looked like a nominal clause and not a main clause, to my uneducated eyes.
I apologize for my confusion, but I do thank you very kindly for all your wonderful help!