I wish containers hadn't created the abstractions of a registry and an image instead of exposing it all as tar files (which is what it kind of is under the covers) served over a glorified file server. This leads to people assuming there's some kind of magic happening and that the entire process is very arcane, when in reality it's just unpacking tar files.
If you want to DIY a container with unix tools, this should help: https://containers.gitbook.io/build-containers-the-hard-way/