Once the flash is complete, tap "Reboot System". The first boot can take anywhere from 5 to 10 minutes as the system builds its cache. Be patient! If the boot takes longer than 15 minutes, you may need to force a reboot or redo the wipe and flash.
Flashing a custom ROM requires modifying your device’s core system software. This process carries inherent risks. samsung s3 custom rom android 10 link
Before altering your device partition table, you must acquire specific open-source components: Once the flash is complete, tap "Reboot System"