Yeah, IIRC, that’s right for the 3×3 one, anyway – the 6 faces that go straight out are attached to the core.
Ok, I broke down and watched a videos. At least some 3×3 cubes have no ball in the center, but a 6-spoke thing holding onto the center faces.
The 4×4 has a more ball-like center, though it’s made of several parts.
On the 4×4s, all the faces can be removed.
SO, to answer the original question, it’s involved – you want to get the corner pieces right, and assemble sections before attaching them, perhaps with the help of some tape.
Here’s one video on it. There are many such videos about doing it. https://puzzles.wonderhowto.com/how-to/disassemble-and-reassemble-4x4-rubiks-cube-puzzle-270547/