|In addition to making my own sewing sample collection (which is then attached to a metal ring), I have also collected sewing samples from RTW (ready-to-wear garments).
I either use clothing that I no longer want or I will seek out clothing at thrift shops and then I snip out the section that I want.
Example - I cut out various zipper flys from pants . I have collars of all types, pockets, cuffs, hems, etc.
I store all of these in a box for future reference. The nice thing is that it's always there and I don't have to go to my own closet to see how something is made. I also have a wide variety to chose from and I can study how professionals construct them.
You can learn so much.
Is there a collar that has a sharp corner but your always resemble "dog ears"? You can deconstruct the collar partially to see just how they managed to do it.
While in design school, I purchased several European designer jackets (original cost in the hundreds!) at a thrift shop and took them apart to learn how they were constructed and interfaced. It was quite an education and I still have those jackets decades later and use them in my classroom lessons.