Depends on what your minelayer is capable of launching each turn. With the current patch, a minelayer with nothing but mine layer components holding mines (none of those cargo bays with one mine layer ships in other words) can launch half of its full mine complement.
Essentially, you have to move the mine layer so it's more than one turn away from the launch point. Tell it to remote launch mines. Order it to move a point that is more than half the movement of the minelayer and then tell it to remote launch back at that point. Then give it orders to pick up more mines at whatever planet you have building and/or storing mines and set it for repeat orders. So long as that planet keeps building mines, the minelayer will keep picking them up, move to the launch point, launch the first half, move away from the launch point and launch the rest next turn.
Personally, I edited the mine layer components so they'd be able to launch a full load of small mines in one game turn since that extra dogleg away and back to the launch point was too annoying.
