FreeBSD: Unable to find device node for dev /dev/ar0s1b in /dev

Problem:
Sysinstall can't continue and stops with the error, "unable to find device node for dev /dev/ar0s1b in /dev".

Solution:

Remove the existing partition table by writing zeros at the start of the disk:

dd if=/dev/zero of=/dev/ar0 bs=64k count=1

(replace as necessary, e.g., ad0)