I’m doing a practical guide on the basis of Lal posts (and overall my own understanding at this point) so I may post that step-by-step in the future (at the Anagami stage, if that will happen of course)
Right now after Sotapanna you need to contemplate the aspect of “attachment” to holding things or “having” things via Tlakkhana, you can develop samadhi on any kind of object but chanting is the best and most easy because it does not need heavy concentration. Here are examples:
https://www.youtube.com/watch?v=DBf9dkqTBd8 (put subtitles on)