A
B
a
A
b
A
B.
The A & B are repeated, usually exactly but not necessarily. So to do it for yours you could start like this.
Packing crates and palings mark the place of their demise.
row on row across the tortured soil.
.....................................( line to rhyme with ise )
Packing crates and palings mark the place of their demise,
........................................( line to rhyme with ise )
.........................................( line to rhyme with soil )
Packing crates and palings mark the place of their demise,
row on row across the tortured soil.
By coming back to the repeats it makes it more complete. I think. And of course the lines to be put in should make some sort of continuation of the sense, not just disconnected to the other lines, so to do that you may need to alter the repeats slightly.
You may wish to ignore my suggestion.
As you wish.
) 
