If your phone can still boot to fastboot, use TWRP (Team Win Recovery Project).
To successfully flash the Huawei P10 Lite, you need three specific things:
This is not a flasher itself, but a necessary utility. Official Huawei firmware comes in a compressed format (Update.app). This tool extracts the individual partition images (system.img, boot.img, recovery.img) so they can be flashed manually.