I have containers on skids/pallets inside a cold frame made out of PVC pipe with the top covered in chicken wire and plastic. I like to keep my containers off the ground because I'm afraid of slugs and other nasties getting in through the drain holes. If you put them on the ground I suggest putting a sheet of plastic under them.

As for drainage, I think if the holes are big enough, and plenty enough, it shouldn't matter where you put them. They'll still drain just fine.

I put holes in the sides of the container as close to the bottom as possible. Just in case they plug at the bottom.
duane

Ground is fine.

I kept mine on the ground with no problems. I just have to keep them away from low spots in the yard (puddles).

I have sought/bought plastic shelving units with vented shelves for my winter sowing jugs/containers. I do a lot (300 last year)and I get less grief from the family if the whole WSing thing is contained better/tidier. "Going Vertical" using the shelving units really helped.

Nancy

I do much like duane does: I put one extra hole on the side, low to the ground, as an emergency drain. About 1/4" size, like the rest of my drain holes.