There are a few main ways to get OoB in Naraku but this is the fastest and most consistent. First, switch to the overhead camera angle as it allows you to see the position of MC's feet which is an important visual queue.

-Find the wall and floor on the first stratum of Naraku that has the wonky geometry (The first pillar on the left) -Walk towards the wall until you are right against it -On the Circle-Pad tap up and slightly left until you can see that your vertical position is lower and you can no longer see the feet of MC -Now tap left to finish clipping out of bounds and move over to the area after the locked door using your map on the bottom screen and stop moving when you reach the area where the hole that drops down to the Fourth Stratum -Begin to tap up and down on the D-Pad to push yourself down faster -Once the game drops you back in bounds jump down the hole