Please read how to build Docker images (docker build). The Dockerfile you need will be something like this:
FROM collabora/code
RUN apt update
RUN apt install <write here the font package names in Ubuntu 16.04 that you need>
# and/or
COPY <font-files> /usr/share/fonts/truetype
RUN su lool --shell=/bin/sh -c "loolwsd-systemplate-setup /opt/lool/systemplate /opt/libreoffice >/dev/null 2>&1"
CMD bash start-libreoffice.sh
I did not try this, so please don’t follow it blindly, and read the Docker manual.