From ancient times and first trials we still carry the folder for "VyOS as Docker container".

https://github.com/vyos/vyos-build/tree/96ff51d3d2e559194f86ea99f817c86d1a1bfd20/docker-vyos

But during normal evolution and while also starting to play using containerlab a new helper was added make oci to produce an OCI image from an ISO image
https://github.com/vyos/vyos-build/blob/96ff51d3d2e559194f86ea99f817c86d1a1bfd20/Makefile#L88-L91

So there is no additional assembly required, after the ISO is generated one can simply make oci to get a proper, importable open container image of VyOS.