Mine have gone in today in pots on the kitchen windowsill. Usually I sow in small seed trays, but I think the deeper root run may be better. Worth a try anyway and I have two pots full, so I might experiment with early transplanting into modules for one and leaving them a bit to grow on for the other.
This year I have Ailsa Craig, having spent a fair bit of the summer casting envious eyes on one of my plot neighbour's crop. He reckons they keep better than Globo as well
You need a cool, bright, frost-free place to nurture the seedlings, so early sowing is not for everyone, but as a dark days of winter mood boost, I would recommend you have a go if you can. I make do with a windowsill in a cool room and then a blowaway mini greenhouse inside an unheated greenhouse, so nothing too special required.
Warning - onion seedlings are slow growing and take ages to get going. This is a pastime for seedaholics and those with patience. The upside is you (usually) grow bigger, better onions that those from sets and get much more choice of types to grow. The last two years have not been great growing seasons, but I have had a crop of some description, while onion sets planted on the plots around me either bolted or withered to nothing.
The thread from last year is here for reference.
Onions from seed - 2018 in Grow Your Own - Page 1 of 9