Chosen Solution

So I recently got a 3DS XL (the old version, not the new version) And the right bottom part isn’t clipped in properly, is there any way you can fix this? (I have tried clipping it in, but it won’t work.)

I think the easiest ways is to remove the bottom cover by removing the screws and then try to clip it back into place. You can follow the first few steps of the battery replacement guide.