# Make mount point directory
root@pie:~# mkdir /ssd

# Find out device UUID
root@pie:~# blkid
/dev/mmcblk0p1: LABEL_FATBOOT="system-boot" LABEL="system-boot" UUID="4D3B-86C0" TYPE="vfat" PARTUUID="4ec8ea53-01"
/dev/mmcblk0p2: LABEL="writable" UUID="79af43d1-801b-4c28-81d5-724c930bcc83" TYPE="ext4" PARTUUID="4ec8ea53-02"
/dev/sda: UUID="13ccd2a1-3e29-4c16-847a-68c52c4c3577" TYPE="ext4"

# Edit /etc/fstab
LABEL=writable	/	 ext4	defaults	0 0
LABEL=system-boot       /boot/firmware  vfat    defaults        0       1
UUID=13ccd2a1-3e29-4c16-847a-68c52c4c3577 /ssd ext4 defaults,auto,users,rw,nofail 0 0