As this image has been pushed to my dockerhub, you can download it:
$ toolbox create -c gst-dev-f39 --image docker.io/philn2/gst-dev:f39
If you prefer to build it yourself:
$ podman build -t gst-dev:f39 .
$ toolbox create -c gst-dev-f39 --image localhost/gst-dev:f39