BEFORE YOU MARK THIS AS A DUPLICATE WITHOUT PAYING ATTENTION.
I have two bootable image files, what I'm trying to do is put them on a flash drive, then do a fresh installation of the grub bootloader so it'll point to those two live operating systems and let me decide which one I want to boot into whenever I plug it into a computer.
I'm not trying to repair my local boot loader, I'm not trying to do a fresh install or setup of an operating system on my local machine.
I have two live operating systems and I split my flash drive up into 3 partitions, sdb2 is one OS, sdb3 is the second, and sdb1 is where I wanted my boot partition to be with my bootloader and everything I'd need to make it happen.
I already ran grub-install and grub-update and grub-mkconfig, but it seems like it keeps installing what would be the bootloader and its configuration for my local machine.
I'm sure there must be a specific way this is done, but all instructions I've seen are vague and the end goal is usually to have grub point to your local os.
I'm not familiar with all the key inner workings of grub when you first install an os and all the different scripts/files it needs and uses to compile itself and configure everything.
I can't get far with it, I at least have it to the point to where my bios can tell that I'm trying to boot to a flash drive instead of immediately redirecting me to my hard drive, but that's about where I'm at.
I've been stuck for about an hour and I need help.
Thanks in advanced for any advice! And please DON'T mark this as a duplicate unless you have an answer that's really solid and directly solves the problem. Like I said, all the other answers and articles I've found haven't been helpful.