This is for the configuration of silo, similar to what is in boot-scripts.
cat > ${CLFS}/etc/silo.conf << "EOF"
# Begin /etc/silo.conf
partition = 1 # Boot partition (= root partition)
root = /dev/sda1 # Root partition
timeout = 150 # Wait 15 seconds before booting the default section
image = /tools/boot/vmlinuz-clfs-4.9.21
label = linux
# End /etc/silo.conf
EOF
If you already have Silo installed on your target system, you do not need to reinstall it. Silo is just a chain loader and has no bearing on the system build.
After you get the build copied to the system that it will boot from, you will need to issue the following command:
silo -f