USB bridge to flash spi for Arduino project

Hello freelancer, I've got a project include ATmega328p and SDcard with audio file on it. The Atmega can read and play sound on the SD Card, that work well. But now I would like to replace the SD card by a SPI Flash, and add a USB connectivity for access to the flash from a computer and give access to change the sound file on the flash through the windows explorator file (like with USB key). I just need a schematic and your recommendation for design. But you have to give me some proof of your working schematic with some example of work you've done. Thank you !