This year I'm staggering the potato planting over about 6 or 8 weeks. They are not all the same varieties, so it's not a real test of when is best to plant them. I just don't want to overdo the garden work by planting them all at one time.
This week I bought another package of Yukon Gold potato sets. They were already quite sprouted. I planted all of them today, and didn't bother to cut the sets into pieces.
This year they are all going into trenches. Last year, I planted more shallow, and hilled up soil around them. I think that makes for drier soil in summer, hence need for more water. In addition, voles got into several of them. This time, we'll see if planting deeper means less watering and less loss to voles.
I'm digging a trench about 1 foot deep, placing the sets into the trench, then covering with a few inches of soil. As they grow, I'll continue to fill in with soil.
I didn't bother to stand the sprouts upright. I doubt that it matters.