In the battle where Kakashi gets his Sharingan from Obito, we last see him being trapped under the rubble where one part of his body is squashed completely,
but during the flashback sequences shown in the manga chapter with Madara and Obito, we see Madara explaining to Obito he slipped through the rubble.
I thought it was an attribute of his Mangekyo Sharingan which makes him perform the teleportation into Kamui's dimension, which he hadn't activated at that point of time. He is shown to activate that in the later chapters, after the death of Rin.
My question is then How did he slip through the rubble?