Gap year for trees – how to make a nursery bed?

In my excitement to expand my food forest to a new area, I got several 1 yr seedlings before realizing that I really should prepare the new area first. So, my trees need a gap year to grow a little on their own first before settling in.

How can I make a smaller scale nursery bed to house the trees until spring or next fall?

If it was just a few weeks, I know I could heel them in. But if I want to buy them more time, what’s a good setup?

My plan right now is to prepare a bed like how I would prepare a new garden bed. Reserve a row, loosen the soil (it’s clay), mix in leaf compost, and mound it up maybe a foot to make it easier to pull out next year. Then mulch with plenty of wood chips to mitigate the higher heat loss over winter from the raised aspect. (Zone 5, winters can get pretty cold here.) Then, plant the trees maybe about a foot apart.

And next time be more patient.

Any alternatives or other suggestions? Thanks.