To start, run the prepare.sh script in this directory by passing it an environment file you wish to template.
cd q2galaxy/docker/
./prepare.sh some_environment_file.yml
This will install an environment in the root of the project and use that to template out your tools.
At the end of this process, the script will echo a docker build command. Adapt this as desired (usually just the image name) and run it.
You should now have a working container.