One thing Apple could do with a flip is to not have if fold entirely in half, leaving maybe 15 mm at the bottom uncovered. That 15 mm wide section could then be made double-thickness, allowing the inclusion of a camera without needing a camera bump.
E.g., the iPhone Air's slab section is 5.6 mm, and the camera bump protrudes by 5.7 mm. Thus they needd 11.3 mm for the camera. So if they made a foldable of that slab thickness, then folded it would be 5.6 x 2 mm =11.2 mm, so the double-thickness strip at the bottom could accommodate the camera while staying nearly flush with the folded phone.
E.g., the iPhone Air's slab section is 5.6 mm, and the camera bump protrudes by 5.7 mm. Thus they needd 11.3 mm for the camera. So if they made a foldable of that slab thickness, then folded it would be 5.6 x 2 mm =11.2 mm, so the double-thickness strip at the bottom could accommodate the camera while staying nearly flush with the folded phone.

