Difference boolean modifier leaving interfaces behind I'm new to blender. I've made a shape consisting of 4 cuboid meshes which have been joined via face-to-face snapping. I then use them to carve (using the boolean difference modifier) from a larger cuboid. I've tried this with and without joining the 4 cuboid meshes first. However, my resultant carved cuboid sometimes has very thin interfaces between carved segments, as if the pieces weren't fully opposed.

How to I get rid of these faces, or ensure they don't appear after carving? I know I could just overlap the original cuboids but the problem is they're both larger than each other in separate dimensions, so it'd look messy.

You can see the very thin shaded interface in the carved object (the selected object).
There are probably precision problems where the compound cuboid components are not truly flush in a numerical sense.

You could try unioning the original cuboids into a single object rather than just joining them.

Alternatively, it looks like you could create the compound object via simple extrusions rather than as multiple cuboids.  This would give you a more consistent form that you could use for boolean operations.