I made some small 1x2 air prune boxes last year and fall sowed a bunch of various seed I had. I then covered the tops with hardware cloth to keep the rodents out and buried them in a wood chip pile for the winter. This spring I have seen some decent germination.
I like the small size so that I can easily carry them around, they also stack up neatly. I’ll prop them up on rocks and/or bricks to get the air gap.
Apples
Hazelnuts
Nemaguard peach
American plum
Mulberry
Juneberry
