Shallots, don't need much 'depth' to grow in, I wouldn't put in a 'tattie bag', you'd have to fill to top as need to be near surface.
I would put them in 'grow bags' or large shallow pots. They are planted just below surface of soil, or with a bit of the top above surface, depending on the variety. I'd also get planted as soon as you can, other wise will 'sprout' and they may not grow properly. Don't worry about the weather, if anything a bit of cold to stat with will help them.
I plant some that need to be planted in winter, November to January. If not planted then will not grow, as need the cold. Those ones will start to grow in Feb. no matter what the conditions are. They can only be stored for about 4/6mts, but by then the 1's planted in March/April are ready, they can be stored for up to a year, if stored properly.
If you want to know how to prepare for storage and don't want to look on Interweb just ask.
More hail and T&L, close to freezing, may put heating back on.................