How do you build this?

[Rstment25]

I followed the steps -
mkdir -p ~/arrow
cd arrow
repo init -u https://github.com/ArrowOS/android_manifest.git -b arrow-12.1
repo sync
wait 2.5 hours no errors as far as I can see

But the file I got in the end is empty ;p I didn't have to rename it even it came as arrow_device-codename.mk
( Although I didn't see it at first in the folder ... I pasted this in terminal : lineage_device-codename.mk -> arrow_device-codename.mk but it did nothing as far as I can tell? It complains about not knowing what that command is. But weirdly after that I finally saw the file arrow_device......mk)

Anyways file is empty and instructions are really not helpful so I have no idea what to do... I am stuck on this step:
Now inside arrow_device.mk
Change “lineage” to “arrow” & “common_full_phone.mk” to “common.mk”
For example:
$(call inherit-product, vendor/arrow/config/common.mk)
Change PRODUCT_NAME value “lineage_device-codename”
( “lineage_beryllium” ) to arrow_device-codename ( i.e, arrow_beryllium )

Everything is empty , so idk if it's telling me to paste this into the file? IF it is it's really confusing I have no idea what am I supposed to change? This ? $(call inherit-arrow_alioth, vendor/arrow/config/common.mk)

:P Looking at stuff after this in the guide it's even more confusing as idk where the device tree is located?
.. it's been a while since A11 release , maybe the steps are dif now?