POSITION defines the location of each vertex relative to the centre of the shape you defined on the first line. You were on the right track with the top quads in that previous piece of code, all that needed touching up were the UVs.
I recieved a nasty error when I planted your brick, so I'm not certain what the problem is with the bottom quads. However, I can tell you that the position is a little screwed up. It should be:
POSITION:
-1 -0.5 -0.5
1 -0.5 -0.5
1 0.5 -0.5
-1 0.5 -0.5
This arranges each vertex to form a rectangular quad.
Also:
----------------top quads:
2
This should probably be 1 for now.