See if this helps...

Here is a link that might be useful: How to plant calla lilys

When in doubt, just lay it on its side. It will still grow normally even if planted upside down, but that's not good for anyone. :)

Ah, I never mess with "righting" many bulbs/roots/tubers such as callas. I tend to plant a LOT of them, such as the time I bought 2000 daffodils, and I often just plant bulbs by trenching, pouring in, and covering. They right themselves quite quickly in the ground through root and stem action. You really won't hurt it if it does end up wrong side up. But, the best advice was above -- if you can't tell, plant it on its side.

Callas tend to sprout roots from the sides as well as the bottom of the bulb. There's often no obvious 'down' as there is with a daffodil, for example. No root plate, as such.

In the ground, they often dig themselves deeper than you planted them so be sure your soil is deeply loosened.

Agree. Plant on its side. And, if you have only one bulb for this season, no worries. They bulk up reasonably quickly.