ZanyPig66 , Hi.
To use a custome docker image with ClearML you need to have that image locally on the machine that is runing the agent. In the experiment you can specify the docker image either via UI (in the Execution -> Container sections)
Or in code like this:task.set_base_docker(docker_image="python:3.9-bullseye")
Also a small clarification:
ClearML doesn't build the docker image itself. You need to have a docker image already built to be used by ClearML