Once the above is done, you can take a look at any of the popular Compiler construction books/resources many of which would be recommended here. One less well-known but comprehensive work is Project Oberon: The Design of an Operating System and Compiler by Niklaus Wirth.
A quick search found this repository of JonesForth which is a literate programming version of a Forth system that describes the code as it goes along. There appears to be source for various targets.
It is a very interesting exercise that shows you a kind of bare minimum requirement way to make a language and provides insights for what is missing to build more conventional languages.