Here is a tip for how to mount Acans.
For Acan Echinata they make their own skeleton so you could leave them as a frag that you got on sand and they will grow fine (They will grow sid of your rock first and after shape of your frag is on. So if they are on sand they will grow flat after side of your frag) but it is better idea to have some support to make skeleton on. So I mount them on a small live rock this way seem to help them easy to put their own skelecton and you know how your frag will grow (Shape of your future colony)
For Acan lord (Micromussa) they do not put their own skeleton they grow like encrusting monti so if you do not mount them on rock they will grow first side and bottom of your frag rock. If you do not mount them fast your future babies might cover all over the rock than no more room to grow. So you must mount them on live rock.
How to mount them there was a nice good post sometime back but I could not search it....
Some drill a hole on mount rock to fit the frag (Most of them just glue on a rock) and glue and finally epoxy. You do not need to you epoxy but this way you could avoid them growing on 90 degree.
Oh, for glue you could buy one from Loctite from Target or Homedepot it is called "Loctite super glue gel control" cheap and safe to use and they have epoxy as well (Much cheaper than one for Aquarium and safe to use)
Good luck