I have been accumulating several pineapple starts.
4 are white pineapples obtained from a neighbor, and 7 are tops from commercial store bought yellow pineapples.
All have been sitting in the bird bath for a few days to weeks and have begun to sprout roots.
I am about to begin preparing a spot to plant them in.
The location I want to put them into is:

1. Full sun exposure
2. The existing soil is only a few [3 to 6" ?] inches deep over lava rock.
3. I am building another 6 to 8" of additional soil by layering mulch and 1-1/2" minus cinders over the existing soil.

I'm thinking that as long as I provide enough nutrients for fruit to develop nicely the location should be good enough.
Any comments?

What kind of spacing should I give them?