I don't know about "modern", but you could go the traditional route and bootstrap it from Assembler (You'll find that you only have to implement a tiny number of primitives until you can start implementing the rest in Forth itself).

Chapter 9 of Leo Brodie's "Starting Forth" is the text that kicked off my implementation in the early 80s (and undoubtedly countless others): https://www.forth.com/starting-forth/9-forth-execution/