Check the earth every few days, take out the eggs and put them in the freezer. As long as the eggs are just a day or so old, its just yolk and no snail yet. It's according to breeders the most humane way. I have 2 Helix aspersa myself, have frozen a bunch of eggs.
I know I sound weird, but I absolutely CAN'T put eggs in the freezer, even if there's no snail yet. I'm going to die if I do this!
What my sister and I do is that we put the babies in specific containers, then when we have time and when it's not too cold, we go in a wood and release them in the wild. Until then, they don't need too much care, just a bit of food and room.
x5 Cepaea nemoralis (Rainbow, Lemonade, Peanut, Cupcake and Berry) x1 Cepaea hortensis (Lemon) Hopes to get snails of other species
R.I.P. Marble, Choco and Cappuccino, also known as the "Brownie Club" R.I.P. Lucky, the little fighter