It's presumed that you're using OOS as the base on both slots.So no usual steps:
Rom+twrp, reboot recovery
Waiting for kernel sauce@darkobas,
I know your are busy with op 7 pro, but we need android q rom for op6, please help us out. I've tried all other android 10 roms for OP6 but they all suck. Kindly help us out. Guys thank this post if you want omni 10.0, for op7 pro its already released.