These are the instructions to flash Stock firmware on Huawei P8 Lite (ALEL21) using the Card update method.
Flash Stock firmware on Huawei Smartphone (Card Update)
Step 1: Create a new folder on your Micro SD Card and rename it to dload.
Step 3: Now Copy UPDATE.APP and paste it the dload folder on your Micro SD card.
Step 4: Now Power Off your Huawei Smartphone.
Step 6: Update Process may takes 5-10 minutes to complete.
Step 7: Once Update Process is completed your device will reboot automatically and ready to use.
Notic: Please keep in mind that, you must flash Huawei P8 Lite (ALEL21) firmware at your own risk and also full responsible with you.