How to mirror and object/ flip an object - no modifier

I want to set my pivot/origin below the mesh on the z axis, then mirror it / flip it so that its the opposite of the top mesh.

The modifier is not doing this

look at the z axis on the pivot, its pointing straight up, the top mesh is the original. the bottom should be flipped opposite. if i tick the x and z axis in the modifier, it just makes another copy

ok, i figured it out, for some reason you have to add your object through the modifier at the bottom, but now its throwing the mirrored object too far down:

edit: how do i remove attachments? i posted wrong picture but wowser its still around!