> want to know more about implementing in a low level language.

You might check out Jonesforth [0], which is an extensively-documented Forth implemented in x86 assembly language. If you read the single source file top to bottom, you'll get a good understanding of how it is implemented. There are also ports to x86-64, ARM, and other machines.

If you're looking for something in C, you might check out Ficl. [1]

[0] https://github.com/nornagon/jonesforth/blob/master/jonesfort... [1] http://ficl.sourceforge.net

This particular chapter talks about implementation. It probably gets you 80%-90% to an understanding of what you need to do, and the rest should be learnable by examining other implementations, now that you know what to look for.