
"Object Oriented Forth" by Dick Pountain is a succinct and practical exploration of applying Forth's metaprogramming capabilities to extend the language with various features. The best aspect of the book is that it works through many alternatives rather than taking a direct path. It's more about data structures and abstraction than OOP.
Julian Noble (https://www.taygeta.com/fsl/docs/NobleArchive.html) also wrote a number of very interesting articles and books about Forth. There's an apparently ongoing project to re-typeset his "Scientific Forth": https://github.com/Josefg/Scientific_FORTH.
The cost is stupidly high, though. Look at the source code of [1].
The only good page to take from OOP book is the automatic and implicit pseudo-variable "self" or "this", that can reduce stack juggling significantly. I've implemented that in my (yet to be published) dialect and it works like a charm. In my experience, you can have that for cheap and anything more is not worth it from the point of view of a byte-counting Forth programmer.