Those bulbs, in my experience, are hit or miss.
I went through about 9 of them before I finally got 3 to sprout, but once they begin growing, they take off.
You really don't need to worry much about placement at this point, if I were you, I'd leave them above the substrate (or plant them on their side) and then once they sprout, just turn that side up and plant about 1/2 the bulb in the substrate.
If you plant them on their side, they'll usually just root where they are so you won't even need to move them once they start growing.
But regardless, the plant will find it's way to the light even if you plant it upside down, it would just take an extra day or two to finally emerge out of the substrate.
Good luck with them, hopefully you get a good batch!