1m high retaining wall build
It depends on soil conditions. I build on the flat many walls with stable soil behind the wall I build flat to flat no mortar straight up but will back fill with pea gravel or river rock to allow it to drain. 

In some cases I will stager each block back a 1/4 or ~ 6mm back this works without mortar with stable ground. 

With the above cases for loose soil that may shift I will mortar in place without pillars. 

I have seen pillars used and rectangular blocks on edge , it was interesting and much less expensive but I did not think it would hold up as well, I cannot say if it has held up as I haven’t been in that town for years. 1 meter is not a lot but it depends on soil conditions and I like free standing blocks or rail road ties pinned together  for small walls so some opinion and some soil conditions make a difference.