An alternative solution... for some definition of the term... is to write a "naive" Dockerfile like RUN foo RUN bar RUN baz and then just build it

An alternative solution... for some definition of the term... is to write a "naive" Dockerfile like RUN foo RUN bar RUN baz and then just build it with something like... I think kaniko did this last I looked?... that smashes the whole thing into a single layer. Obviously that has other tradeoffs (no reuse of layers) but depending on your usecase it can be a good trade to make (why yes, I did cut my teeth in an environment where very few images shared a base layer, why do you ask?).