[Google Pixel XL Questions & Answers] obsidianlycanthrope:
Following instructions from there, and also trying a different cable. I have the same issue, it still bootloops.

C:\Users\Obsidian>cd C:/platform-tools

C:\platform-tools>fastboot devices
HT6A30206491 fastboot

C:\platform-tools>flash-all
Sending 'bootloader_a' (32424 KB) OKAY [ 0.842s]
Writing 'bootloader_a' (bootloader) Valid bootloader version.
(bootloader) Flashing active slot "_a"
(bootloader) Flashing active slot "_a"
OKAY [ 16.264s]
Finished. Total time: 17.268s
rebooting into bootloader OKAY [ 0.015s]
Finished. Total time: 0.015s
< waiting for any device >
Sending 'radio_a' (57140 KB) OKAY [ 1.793s]
Writing 'radio_a' OKAY [ 0.852s]
Finished. Total time: 2.791s
rebooting into bootloader OKAY [ 0.010s]
Finished. Total time: 0.011s
extracting android-info.txt (0 MB) to RAM...
--------------------------------------------
Bootloader Version...: 8996-012001-1811131534
Baseband Version.....: 8996-130181-1811270246
Serial Number........: HT6A30206491
--------------------------------------------
Checking product OKAY [ 0.050s]
Checking version-bootloader OKAY [ 0.049s]
Checking version-baseband OKAY [ 0.049s]
extracting boot.img (30 MB) to disk... took 0.795s
archive does not contain 'boot.sig'
archive does not contain 'boot_other.img'
archive does not contain 'dtbo.img'
archive does not contain 'dt.img'
archive does not contain 'odm.img'
archive does not contain 'product.img'
archive does not contain 'product-services.img'
archive does not contain 'recovery.img'
archive does not contain 'super.img'
extracting system.img (1953 MB) to disk... took 14.468s
archive does not contain 'system.sig'
extracting system_other.img (312 MB) to disk... took 1.951s
archive does not contain 'system.sig'
archive does not contain 'vbmeta.img'
extracting vendor.img (259 MB) to disk... took 1.690s
archive does not contain 'vendor.sig'
archive does not contain 'vendor_other.img'
mke2fs 1.44.3 (10-July-2018)
Creating filesystem with 29939712 4k blocks and 7487488 inodes
Filesystem UUID: 370a14d6-4260-11e9-a75f-5fe718f1534e
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000, 23887872

Allocating group tables: done
Writing inode tables: done
Creating journal (131072 blocks): done
Writing superblocks and filesystem accounting information: done

Sending 'boot_a' (31001 KB) OKAY [ 0.801s]
Writing 'boot_a' OKAY [ 0.603s]
Sending sparse 'system_a' 1/4 (524284 KB) OKAY [ 12.109s]
Writing sparse 'system_a' 1/4 OKAY [ 3.998s]
Sending sparse 'system_a' 2/4 (524284 KB) OKAY [ 11.960s]
Writing sparse 'system_a' 2/4 OKAY [ 3.952s]
Sending sparse 'system_a' 3/4 (524284 KB) OKAY [ 11.916s]
Writing sparse 'system_a' 3/4 OKAY [ 4.045s]
Sending sparse 'system_a' 4/4 (427564 KB) OKAY [ 9.706s]
Writing sparse 'system_a' 4/4 OKAY [ 3.348s]
Sending 'system_b' (319668 KB) OKAY [ 7.904s]
Writing 'system_b' OKAY [ 2.646s]
Sending 'vendor_a' (266192 KB) OKAY [ 6.558s]
Writing 'vendor_a' OKAY [ 2.295s]
Setting current slot to 'a' OKAY [ 0.406s]
Erasing 'userdata' OKAY [ 29.008s]
Sending 'userdata' (4672 KB) OKAY [ 0.196s]
Writing 'userdata' OKAY [ 0.206s]
Rebooting
Finished. Total time: 136.871s
Press any key to exit...