Oh, it's easy --

You'll get a piece of bamboo that's thick & curved at the ends, and flattens & widens to its center. Fold it so the curved ends enclose a small metal tube with cork on it, then start wrapping them together with string & glue. Then, go to the thin, folded end of the reed, and trim it off to create the opening for air to go through. Now, lightly shave & shape the flat outside surfaces, making some areas thinner and leaving thickness in others to give some structural support to manage the buzz of the thin areas. Work it until it gets a good "crow" -- buzzing a pitch without being in an oboe -- at about a concert A (I think). If you can't get it to buzz, and/or you've trimmed & cut it so much that it buzzes above an A, it's FUBARed and you need to start with a new one.

Well, that was all from memory, going back to flute-double reed class in college. A bassoon reed is almost the same, except that it's broader and doesn't have the metal tube & cork.

Here's a how-to. It goes into a LOT more detail than I cared to remember.
https://everything2.com/index.pl?node_id=1295338

RMP: How is the recovery going? Tomorrow it will be three weeks for me. I've ridden quite a bit (not as much as usual, obviously). I am not 100%, but I am feeling better. My groin is getting some of the feeling back, and so I feel some stretching, puliing, tingling sometimes. The balls remain a little tender. I am eager for that to go away. The scar is looking quite good--much better than the scar I had from a previous surgery 27 years ago. I suspect that for the most part the hair will cover it up. I don't have to go back to the doc. I recommended to him that he tell patients to keep things supported after surgery. That really helped me. And I told him that they should do a better job of shaving. One of the worst moments in the ordeal was when I had to take the bandage off. Ouch!