[Help] Trying to install Ventura on Macbookpro 12’1 won’t boot unless usb is installed.

So I’ve followed one of the many guides to install macOS Ventura on my 2015 MacBook Pro 12’1 I have gotten it to install. Problem is my Mac won’t boot unless I have the flash drive installed. The hard drive shows but when I try opening it it shows a circle with a line going through it for Apple support. When I have the flash drive installed it shows the efi boot and it boots normally how can I fix this? It’s a clean install