Mound Gardening in the North
The problem with gardening in the North is the cold soil temperature. Years ago I read about a method used in Scandinavia which I believe is called mound gardening. I did this type of gardening for some years while we live in the Northwest United States and found it to be very simple and effective.
The method requires that you have some tree branches, trimmings work perfectly. I used poplar and wisteria but I am sure any deciduous branches would work. I am not sure about evergreens. You take your branches and lay them out lengthwise in a long mound over untilled soil. Then for the next year you add all of your compost material to the mound. The air flow through the branches keeps the compost from getting too hot so you don't need to turn it. Just keep adding all the garden and kitchen vegetable waste through the year. Don't forget the autumn leaves.
When spring time comes cover your composted mound with a four to six inch layer of good garden soil. The aerated compost underneath will continue to provide warmth throughout the growing season. Plant your crops as usual and enjoy the excellent results.
Each year you start a new mound trading locations as you go. You'll find that the soil underneath your two year old mound is beautifully enriched and friable so that is what you'll use to top your new mound. Use the remaining material from old mounds to improve your new mounds.
This turns out to be an easy and effective way to improve the soil in your garden while you are enjoying good crops. This method is easy to start and it just get easier. I found my soil so improved that after about ten years I stopped mounding my garden at all except for growing melons and tomatoes which require good warmth.
Additionally a plastic tent over a mound garden provides even more warmth for tomatoes and peppers. You could do your mounds in boxes but I never did. A box frame would make it easier to place flexible PVC for a tent frame however.