How can I set my custom base folder to one on a flash drive for Mac?

Hi! Disclaimer: I do not have a lot of experience with tech, so I would really appreciate detailed directions. My local drive on my Mac is running out of space, and I have a lot of audio/image files on my flashcards. I would like to move Anki and its sub-folders to a flash drive so that I don’t have to worry about space. I know that I am able to set a custom base folder, which if I understand correctly changes the folder for which new media will be copied and referenced from. However, I assumed the information on the doc is for users wanting to set a custom base folder already on their local drive. Furthermore, the section on using Anki with a flash drive only covers Windows machines. How would I be able to set my custom base folder to a flash drive? Is there an addendum I must reference when using the command in terminal? Thank you!!