I have these hatch all of the time. A good way is to take pvc piping about 1" to 3" diameter and saw 1.5" pieces of it in half. Place a few of these with the rounded side up (like little tunnels) behind your rockwork.
The snails will sometimes spawn underneath them and there is a good chance they will go unmolested. I have astrea snails that reproduce and mature in my tank. I also have cerith snails that reproduce but don't seem to mature above 2-3mm.