On the rack, we stacked flat, except for the tie row on top. I always liked to put the first three across the back lengthwise and flat for stability and then put the rest of the tie row crossways on edge- figured I got an extra bale on and easier to grab the top row when unloading.

In the barn, we always stacked on edge- didn't fuss with cut side up or down. An experienced man can build a much tighter surface for walking and no fuss dropping them in tight- you learned how to drop them so they kinda 'rolled in' tight. Stacking bales flat leaves nothing but a series of holes to fall into.

In high school, working for neighbors, sometimes they would get some 'warm bodies' and put them in the barn. They only knew how to stack bales flat. They'd wear themselves and me out with the poor job they would do. I'd rather work with one guy who knew his stuff than three that didn't.