See: http://www.raspbsd.org/pine64.html
Step 1: (This step is currently optional)
First step in creating a FreeBSD image for the Pine64 is building a u-boot with the CONFIG_API option enabled.
This is needed for ubldr.
See https://github.com/tomtor/u-boot-pine64/tree/freebsd and https://github.com/longsleep/build-pine64-image/tree/master/u-boot-postprocess for build instructions.
https://github.com/tomtor/image-freebsd-pine64/raw/master/build/u-boot-with-dtb.bin is a ready to use version.
Step 2:
Run the mkimage.sh script, but check the settings in this script first!