Think the initial attempts were in a V of Vs, pretty common to bomber formations everywhere. Then, a guy name LeMay, worked out the combat box formation where there were high, medium and low squadrons in a group, each offset from the other squadrons in a step down fashion. It was a fairly novel idea and allowed more of the sky to be covered by each bomber's defensive fire.
The effectiveness of the "Combat Box" (also known as the Bomber Box) varied between units. Some units flew a very tight one, others more loose. Correspondingly, tight groups tended to be left alone by the Luftwaffe while loose groups were attacked more often. But tight group might have a higher percentage of collisions and fratricide.
It was a double edged sword.