insert into /etc/rc.conf the following code: (e.g. 4x Intel NICs bond together in LACP-Mode)
# tested under FreeBSD v10.x and v11.x
ifconfig_igb0="up"
ifconfig_igb1="up"
ifconfig_igb2="up"
ifconfig_igb3="up"
cloned_interfaces="lagg0"
ifconfig_lagg0="laggproto lacp laggport igb0 laggport igb1 laggport igb2 laggport igb3 192.168.0.1 netmask 255.255.255.0"