Werken mit dem Taschenmesser ("Working with a Pocket Knife") is a Swiss book, published by AT Verlag and apparently sponsored by Victorinox, the famous Swiss army pocket knife company. The idea of the author Felix Immler is to make many (twenty six) objects from wood found in the forrest and worked only with a (multi-tool) pocket knife. After a part dedicated to learning the different knife tools usage, the tutorials, range from "beginner" to "expert". This last section features a Nasenflöte.
Seven pages are dedicated to the nose flute making, but I obviously cannot publish them "full size", for copyright reasons. However, let's take the risk to show some pictures, as advertising samples.
As you can see, the tutorial is fully illustrated, with explicit pictures. The texts also are clear and precise, as far as you read German or, as I did, scan them, pass the result through an OCR tool, then stuff Google translation with. The description of the work is precise, providing dimensions etc.
Even if you don't feel the need to rush in the woods with your pocket knife with the irrepressible need to carve a nose flute, the method provided by Felix Immler can be very useful for those of you who would like to take the time to build their own wooden nose flute, in the comfort of a workshop and with the help of precise tools.
You can buy
Werken mit dem Taschenmesser directly from the publisher (here) or cheaper from Amazon (new or used), particulary the German one.
Here is the video supplied in complement of the book: