While the with-ltk macro is the most convenient way to run Ltk, you can do it manuall, especially if you want to play with the Ltk objects in the REPL. To start Ltk you just need to call:
(start-wish)which starts the Tk sub process and initializes the stream to communicate with it. Now you can create and use any Ltk objects. To enable event handling call
(mainloop)which is responsible for event handling. You can interrupt it any time you like, call any lisp function and restart it again.