[Nokia 6.1 (2018) Guides, News, & Discussion] prg318:
Use the "extracted" image (should have a bunch of .elf, .img, and .mbn files). Then you need to execute a bunch of fastboot commands for each partition.

You'll have to adjust the commands somewhat to work with the image that your flashing but you can get an idea of what needs to be done from this script:

@echo off
cls

cd /d %~dp0
fastboot oem alive
fastboot flash xbl_a B2N-0-132E-xbl_service.elf
fastboot flash xbl_b B2N-0-132E-xbl_service.elf
fastboot flash abl_a B2N-0-132E-abl_service.elf
fastboot flash abl_b B2N-0-132E-abl_service.elf
fastboot reboot-bootloader

echo.
echo Waiting for device...
@ping localhost -n 5 >nul
echo.

fastboot flash partition B2N-0-132E-gpt_both0.bin
fastboot flash xbl_a B2N-0-132E-xbl_service.elf
fastboot flash xbl_b B2N-0-132E-xbl_service.elf
fastboot flash abl_a B2N-0-132E-abl_service.elf
fastboot flash abl_b B2N-0-132E-abl_service.elf
fastboot flash tz_a B2N-0-132E-tz.mbn
fastboot flash rpm_a B2N-0-132E-rpm.mbn
fastboot flash hwcfg B2N-0-132E-hwcfg.img
fastboot flash hyp_a B2N-0-132E-hyp.mbn
fastboot flash pmic_a B2N-0-132E-pmic.elf
fastboot flash keymaster_a B2N-0-132E-keymaster64.mbn
fastboot flash cmnlib_a B2N-0-132E-cmnlib.mbn
fastboot flash cmnlib64_a B2N-0-132E-cmnlib64.mbn
fastboot flash dsp_a B2N-0-132E-dspso.bin
fastboot flash devcfg_a B2N-0-132E-devcfg.mbn
fastboot flash sec B2N-0-132E-sec.dat
fastboot flash mdtpsecapp_a B2N-0-132E-mdtpsecapp.mbn
fastboot flash storsec B2N-0-132E-storsec.mbn
fastboot flash systeminfo_a systeminfo.img
fastboot reboot-bootloader

echo.
echo Waiting for device...
@ping localhost -n 5 >nul
echo.

fastboot flash modem_a B2N-1-132E-NON-HLOS.bin
fastboot flash mdtp_a B2N-0-132E-00CN-mdtp.img
fastboot flash boot_a B2N-0-132G-00CN-boot.img
fastboot erase boot_b
fastboot flash system_a B2N-0-132E-00CN-system.img
fastboot flash system_b B2N-0-132E-00CN-system_other.img
fastboot flash bluetooth_a B2N-0-132E-BTFM.bin
fastboot flash persist B2N-0-132E-00CN-persist.img
fastboot erase userdata
fastboot flash sutinfo B2N-00CN-001-sutinfo.img
fastboot flash nvdef_a B2N-0-132E-NV-default.mbn
fastboot flash hidden_a C1N-0-0020-0001-hidden.img.ext4
fastboot flash cda_a B2N-00CN-007-cda.img
fastboot erase ssd
fastboot erase misc
fastboot erase sti
fastboot flash splash_a B2N-00CN-007-splash.img
fastboot erase ddr
fastboot flash KEY_INFO B2N-00CN-006-keyinfo.img

:flash_vendor
fastboot flash vendor_a B2N-0-132E-00CN-vendor.img >log.txt 2>&1
find /i "FAILED" log.txt
if %errorlevel% NEQ 0 (
echo OKAY
) else (
echo WRITE FAILED REFLASHING...
call:flash_vendor
)

fastboot flash xbl_a B2N-0-132E-xbl.elf
fastboot flash xbl_b B2N-0-132E-xbl.elf
fastboot flash abl_a B2N-0-132E-abl.elf
fastboot flash abl_b B2N-0-132E-abl.elf
fastboot oem set_active _a
fastboot oem enable-charger-screen

:flash_e2p_package
fastboot flash e2p_package B2N-0-132E-e2p.tar >log.txt 2>&1
find /i "FAILED" log.txt
if %errorlevel% NEQ 0 (
echo OKAY
) else (
echo WRITE FAILED REFLASHING...
call:flash_e2p_package
)

:flash_e2p_script
fastboot flash e2p_script B2N-0-132E-e2p.sh >log.txt 2>&1
find /i "FAILED" log.txt
if %errorlevel% NEQ 0 (
echo OKAY
) else (
echo WRITE FAILED REFLASHING...
call:flash_e2p_script
)

:flash_md4
fastboot flash md4 md4.dat >log.txt 2>&1
find /i "FAILED" log.txt
if %errorlevel% NEQ 0 (
echo OKAY
) else (
echo WRITE FAILED REFLASHING...
call:flash_md4
)

echo.
echo rebooting device...
echo done!
del log.txt
pause
exit