Instructions
This print consists two parts
Creating the QR Code .STL
https://printer.tools/qrcode2stl/
Create the QR code according to these instructions
The areas marked in red must either be adjusted as shown in the screenshot or controlled. This is important so that the QR code fits into the case.
You can create the QR code either as plain text or directly as SMS message. I would recommend plain text with the cell phone number because this way you can also use country codes e.g. +81 12345678. The direct SMS QR code unfortunately cannot do this (at least on my cell phone).
Important:
Use as little information as possible in the input field, for example just your number
"+81 12345678".
The more information you enter, the larger the QR code will be, making it harder to print and possibly unreadable.
Generate the .STL and Download it, of course it is free.
For the Case: