OTG integration

Hello, I want to integrate a cryptomator folder, stored on a USB-Stick and plugged in as an OTG Stick in my android 7 mobile phone. Unfortunately I can copy the folder with the help of explorer software to the phone but can´t open or integrate the folder on the usb Stick directly in the cryptomator app. Does anybody knows a propper way to do this? Many thanks for your help and ideas says
Detlef from Germany

Please help me in making a bootable pendrive. I want to know how to make a bootable pendrive.

Following this tutorial, you should be able to access Cryptomator vaults stored on external devices like USB flash drives: How to get access to a vault stored on external device like SD card

@Jeff_K_Daniel is that what you mean by “bootable pendrive”?