Yep always make sure they are secured to wood or rocks with it's roots free in the water via an elastic band or something, they should never be covered, I once put an anubias in the crook of a piece of bogwood hoping it would stay until rooted it didn't so I put a little stone onto the roots to keep it put but it just died, I now just secure them with bands and once they grow new roots and adhere to the wood etc you can remove the band I just got some anubia minima today they are lovely plants
I've heard of anubias just being placed on the substrate with the rihozome exposed, though I'd attatch it to something like rock or wood. Cotton, fishing line and elastic bands are 3 ways to do it, though I've also read about a particular type of superglue being used too
I had an anubias with a huge root structure and I pushed the roots down into the gravel but left the rhizome exposed. It did great for over a month. I eventually stuck it to wood though.
sorry for dragging this back up guys but can i use any super glue? is there a certain brand you use? and can i use this to also fix other things to wood i.e. moss?