I was not raised in a German-speaking city nor in a German-speaking family nor do I claim that what I'll say is empirically supported in a scientific sense, but I think I might help learners of German with an explanation of what I do to interpret "machen" and "tun".
My first step consists of recognizing the structure of the clause. Clauses such as "Tu es in den Ofen!" (Put it in the oven!) and "Mach es gerader!" (Make it more straight) have complements such as "in den Oven" and "gerader", which serve as hints for interpreting what is meant. These are the easiest cases. Interpreting and formulating such clauses becomes trivial once one learns that putting things in places can be represented by process terms such as "tun", "packen", "stellen", "legen", and "hängen" and that shaping and coloring things can be represented by the process term "machen".
However, there are meanings of "machen" and "tun" that cannot be inferred based solely on clause structure. For this reason, it is useful to know them beforehand in order to give two or more interpretations to clauses such as "was machst du?" (What are you doing? / What are you making?).
On the one hand, questions such as "Was hast du getan/gemacht?" (What have you done?), "Was tust/machst du gerade?" (What are you doing?), and "Was tust/machst du Feitag Abends?" (What will you do Friday night?) allow two interpretations: the person making this question may want to know whether you have done, is doing, or will do something or what kind of activity/action you have done, is doing, or will do. Independent of which interpretation is more adequate in the situation, for this meaning, "was" (what) in "was hast du getan/gemacht?" (What have you done?) and "nichts" (nothing) in "ich habe nichts getan/gemacht" (I haven't done anything) stand for an activity/action. When the action kind is what is being asked for, a valid answer such as "ich koche gerade" (I'm cooking) depicts the action that was, is being, or will be performed, and, for this reason, does not include the process terms "tun" and "machen".
On the other hand, in clauses such as "ich mache/backe Kekse" (I'm making/baking some biscuits), "ich mache/koche eine Suppe" (I'm making/preparing a soup), "ich mache/bastle ein Krokodil" (I'm making/creating a crocodile [out of paper]), and "ich mache/zeichne ein Haus" (I'm making/drawing a house), "machen" represents a creative process. For this reason, in the question "was machst du?" (what are you making?), "was" (what) stands for the thing being created. And since what is asked is the kind of thing being created and not the kind of action being performed, the answer may be a simple mention of the thing as in "Kekse" or it may contain the same process term as in "gerade mache ich Kekse" (right now, I'm making biscuits).
I hope this explanation solves your issue.