Boot from ssd

[Basher52]

I wanna use an SSD to boot from on my RaspPi 3B+
I installed ArchArm on an SD and that worked but wanna use a lager disk
and since 3B+ is supposed to be able to boot from USB I figured why not
as I have plenty of those.

I did the same thing installing Arch as on the SD card to the SSD but it just
won't work.
I even tried the bootcode.bin thing to an SD but still nothing.

Not even a beep from the green LED (disk activity LED?)

What am I doing wrong?