I was experimenting with an idea and /boot was put on the first 256MB of a 1GB flash drive.

Windows destroyed the whole scheme when trying to add an NTFS partition after it in the unallocated space.

Can I make a new /boot without having to reinstall? The rest of the partitions are untouched and in perfect working order.

Please note that it's not the Master Boot Record that was destroyed, but the entire /boot partition. So this problem cannot be solved just by reinstalling the GRUB2 boot loader.