Boot from usb stick

Hello,

I'm new with Alpine and tried to boot it at my mini server APU board (http://www.pcengines.ch/apu.htm).
Like done with other linux distris before I write the iso to usb stick with dd and boot it.
Also tried to build a boot stick by following the wiki article http://wiki.alpinelinux.org/wiki/Create_a_Bootable_USB.
Both without success.

Any experience with pcengines APU board?How to fix that problem?

Regards