Heres how I did it slightly differently (including pics) and its the only way that worked for me so far after trying a few other methods without success
Materials used-Tupperware container (cheap one), a big sponge
1) Poke some small holes in the top of the container lid.
2) I cut two small pieces off the sponge about 1 1/2" thick and the length of the sponge about 4".
3) I dipped the sponge for the bottom in tank water and then squeezed out so it remained only damp not dripping wet.
4) I placed that sponge on bottom of container than I placed other dry sponge piece on top.
5) Put the clutchs on the top sponge, and cover container.
6) Place container on top of tank light where its warmest, this causes condensation and keeps the container at a good temp.
7) Be sure and check and when ready help clutch hatch or when you see baby snails move them to tank.