1 - Reboot to recovery
2 - Wipe -> Format Data -> Type "Yes"
3 - Flash OOS (this will flash it on one slot)
4 - Flash TWRP
5 - Reboot to recovery
6 - Flash OOS again (this will flash on the other slot)
7 - Flash TWRP again
8 - Reboot to recovery
9 - Flash Havoc
10 - Flash TWRP
11 - Reboot to recovery
12 - Flash Gapps, Magisk, kernel ... etc
13 - Reboot system