I use the "milk jug" method of wintersowing. This protects the jugs a bit from critters, because you wire back on the top half of the cut-up jug, but you leave the cap off so a little rain/snow will get in so it stays wet enough. Then you just put them out in the yard, or on the deck, but it does need to be where the snow falls on them. Also many (not all) seeds like some light, this is another trigger for sprouting, and they seem to get enough light in the jugs. Mother nature does the rest! This is mostly for perennial plants and shrubs, tree seeds, although some annuals do fine too . Tender more tropical seeds and many garden vegetables it is pointless, they want warmth and sprout fast so just sow them in spring.
If you did winter sowing after your yard is frozen solid, probably you should do like Caroline from the frozen north, and leave them warm and moist a few days before putting them outside. Or do it before it freezes, like now. For me in chilly rainy Seattle, I need to get it done in December so they will get enough cold weather, generally here it is above freezing so they have plenty of moistness without being frozen. Some seeds take two years to sprout! These I move under a cedar tree so they don't get too hot in the sun.
Yes you can stratify in a moist medium in the fridge ( vermiculite or perlite or potting soil or just a moist paper towel), and this often works, or some people put the seeds in similar moist medium, seal them in a big plastic bin, and put them outside to be cold. The fridge can be a great choice, with baggies you can stratify lots in a very small space. Some people have experimented with briefly freezing stubborn seeds, they say it can help but I have never tried it.
Long term cold storage of dry seeds can be done in the fridge or even a deep freeze. When they are dry they do not sprout, but go into a sort of hibernation. But the small frost free freezer in your kitchen refrigerator is not a great choice because it will cycle up around freezing a lot.
You are asking all the right questions!
