Boot server in rescue mode and select FreeBSD rescue image, after login fetch sources:

# cd /tmp
# fetch http://ftp.freebsd.org/pub/FreeBSD/releases/amd64/13.1-RELEASE/base.txz
# fetch http://ftp.freebsd.org/pub/FreeBSD/releases/amd64/13.1-RELEASE/kernel.txz

Destroy existing partitions, for example:

gpart destroy -F ada0

Install using something like this:

#!/bin/sh
PASSWORD=fabrik
USER=devops
ZPOOL=zroot
mddev=ada0

gpart create -s gpt ${mddev}
gpart add -a 4k -s 512k -t freebsd-boot ${mddev}
gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ${mddev}
gpart add -a 1m -t freebsd-zfs -l disk0 ${mddev}

sysctl vfs.zfs.min_auto_ashift=12

set -v
zpool create -o cachefile=/tmp/${ZPOOL}.cache -o altroot=/mnt -o autoexpand=on -O compress=lz4 -O atime=off ${ZPOOL} /dev/gpt/disk0
zfs create -V 1G -o org.freebsd:swap=on -o checksum=off -o compression=off -o dedup=off -o sync=disabled -o primarycache=none ${ZPOOL}/swap
zfs create -o mountpoint=none ${ZPOOL}/ROOT
zfs create -o mountpoint=/ ${ZPOOL}/ROOT/default
zfs create -o mountpoint=/tmp -o exec=off -o setuid=off ${ZPOOL}/tmp
zfs create -o mountpoint=/usr -o canmount=off ${ZPOOL}/usr
zfs create -o exec=off -o setuid=off -o compression=lz4 ${ZPOOL}/usr/doc
zfs create ${ZPOOL}/usr/home
zfs create ${ZPOOL}/usr/obj
zfs create ${ZPOOL}/usr/local
zfs create -o setuid=off -o compression=lz4 ${ZPOOL}/usr/ports
zfs create -o setuid=off -o compression=off ${ZPOOL}/usr/ports/distfiles
zfs create -o setuid=off -o compression=off ${ZPOOL}/usr/ports/packages
zfs create -o exec=off -o setuid=off -o compression=lz4 ${ZPOOL}/usr/src
zfs create -o mountpoint=/var -o canmount=off ${ZPOOL}/var
zfs create -o exec=off -o setuid=off ${ZPOOL}/var/audit
zfs create -o exec=off -o setuid=off -o compression=lz4 ${ZPOOL}/var/crash
zfs create ${ZPOOL}/var/db
zfs create -o setuid=off -o compression=lz4 ${ZPOOL}/var/db/pkg
zfs create -o exec=off -o setuid=off -o compression=lz4 ${ZPOOL}/var/log
zfs create -o exec=off -o setuid=off -o readonly=on ${ZPOOL}/var/empty
zfs create -o atime=on -o exec=off -o setuid=off -o compression=gzip ${ZPOOL}/var/mail
zfs create ${ZPOOL}/var/spool
zfs create -o exec=off -o setuid=off -o compression=gzip ${ZPOOL}/var/spool/clientmqueue
zfs create -o setuid=off -o compression=lz4 ${ZPOOL}/var/tmp
zfs create ${ZPOOL}/var/ports
zfs create -o mountpoint=/jails ${ZPOOL}/jails
zfs create ${ZPOOL}/jails/base
zfs create -o exec=off -o setuid=off ${ZPOOL}/jails/base/tmp
zfs set quota=10G ${ZPOOL}/jails/base
zpool set bootfs=${ZPOOL}/ROOT/default ${ZPOOL}


/usr/bin/tar -C /mnt -x -f /tmp/base.txz
/usr/bin/tar -C /mnt -x -f /tmp/kernel.txz

chroot /mnt pw useradd ${USER} -m -G wheel -s /bin/csh -h 0 <<EOP
${PASSWORD}
EOP

touch /mnt/etc/fstab

# /boot/loader.conf
cat << EOF > /mnt/boot/loader.conf
autoboot_delay="-1"
beastie_disable="YES"
boot_multicons="YES"
console="comconsole,vidconsole"
hw.broken_txfifo="1"
hw.memtest.test="0"
hw.vtnet.mq_disable="1"
kern.geom.label.disk_ident.enable="0"
kern.geom.label.gptid.enable="0"
zfs_load="YES"
EOF

# /etc/rc.conf
cat << EOF > /mnt/etc/rc.conf
zfs_enable="YES"
gateway_enable="YES"
hostname="fabrik" # change to your desired hostname
ifconfig_DEFAULT="SYNCDHCP"
clear_tmp_enable="YES"
dumpdev="NO"
ntpd_enable="YES"
ntpd_sync_on_start="YES"
sendmail_enable="NONE"
sshd_enable="YES"
syslogd_flags="-ssC"
EOF

cp /tmp/${ZPOOL}.cache /mnt/boot/zfs/zpool.cache
zpool export ${ZPOOL}

Reboot and in the https://panel.op-net.com/ set server back to boot in normal mode