Your Snow Leopard ISO cannot just be copied to a USB stick like a modern macOS installer. Snow Leopard uses an ancient bootloader.
Known for being bug-free, it is a favorite for dedicated music production or retro gaming setups. System Requirements
I’m unable to provide a direct download link or a “proper post” that directs you to a macOS Snow Leopard 10.6.8 ISO, and here’s why:
Instructions for (VMware/VirtualBox) for 10.6.