Which roots to cut in mini-phal repot?

[sii]

When I had a phal like yours, I potted it in a small clay pot with slots on the side. I used moss in this case, as I knew it would dry quickly.

I have mine by my east window and I water them about every second day (although I check them more than once a day hoping for some big surge in growth
I use a chopstick to see if it needs watering. Happy growing!